The twelve-year-old Aang is the last surviving Airbender, a monk of the Air Nomads' Southern Air Temple. He is also the current incarnation of the Avatar, the spirit of the planet manifested in human form. As Avatar, Aang can control all four elements and is tasked with keeping the Four Nations at peace.
After fleeing his home and spending a century in a state of suspended animation, he is freed by Southern Water Tribe members Katara and Sokka, who then join him on a quest to to master the elements, and save their world from the war waged by the imperialist Fire Nation.
Aang, the current incarnation of the Avatar, was born upon the dead Avatar Roku, the previous Avatar incarnate. During his childhood, Aang was housed, raised and educated at the Southern Air Temple hidden in the Patola Mountain range--one of the four Air Nomad temples. In early childhood, the temple elders discovered Aang was the next Avatar when in a ritual test, he chose four specific toys out of thousands, mimicking the Tibetan Buddist ritual to find the reincarnation of the Tulku Lama. These four toys--a string-powered propeller, a clay turtle flute, a wooden Hog-Monkey and a wooden hand drum -- were those chosen by past incarnations when they were children, each symbolic of a given element. (air, water, earth and fire, respectively) As Aang grew older, the temple elders kept him ignorant of his status, and fostered his natural Airbending talent through vigorous training. As a result, Aang achieved mastery of Airbending at the young age of twelve, illustrated by his invention of a new Bending technique: the Air Scooter, a large, moving ball of air ridden by balancing on its top.
On a trip to the Eastern Air Temple, Aang was given his flying bison Appa, who became a close friend and the primary mode of transportation for himself and his party. In keeping with his people's nomadism, Aang travelled the world on Appa's back, making new freinds from different nations, and becoming well-versed in their cultures and customs.
Shortly after Aang achieved mastery, the temple elders revealed to Aang his status as the Avatar. Usually, the Avatar is told of his/her true identity only after turning sixteen. However, the monks, fearing imminent war with the Fire Nation, knew the Avatar would soon be needed to help maintain balance. After the revelation, Aang soon began to feel overwhelmed with the burden of his position. His peers ostracized him for his unfair advantage in airbending skill, while his caretakers pressured him to mature into his responsibilities too quickly for Aang's liking.
The only monk sympathetic to Aang's feelings was the elder Monk Gyatso, Aang's airbending mentor, guardian and father-figure. When the burden weighed heavily on his favorite student, Gyatso offered respite through jokes and games. Though Gyatso believed that Aang should be allowed a comparatively normal childhood, the other elders disagreed. Citing Gyatso's attachment to the boy as an interference in Aang's training, they overruled Gyatso, and decided to send Aang away to the Eastern Air Temple, oblivious to the fact that Aang had eavesdropped on their caucus.
Confused and frightened by what he'd learned, Aang fled from his home with Appa. While flying over the ocean, turbulence from a sudden storm caused Appa to crash into the sea. Reflexively placed in the Avatar state, Aang used waterbending to freeze Appa and himself in an ice sphere, putting them in a state of suspended animation in the icy waters surrounding the South Pole.
Soon after Aang's disappearance, the Fire Nation staged a genocidal assault on the Air Nomads. The Air Temples were stormed and the monks and Air Nomads slaughtered in an effort to break the Avatar Cycle and kill Aang before he reached maturity. Ironically, Aang's entrapment in stasis spared him from the massacre, leaving him as the last known Airbender in existence.
Book One: Water
Aang and Appa, having spent nearly one hundred years in an iceberg, were accidentally freed by Katara, a young waterbender from the Southern Water Tribe, and her brother Sokka, the de facto leader and protector of their tribe in the absence of their father. Aang, unaware that a hundred years have passed, is told by Katara and Sokka of the war waged by the Fire Nation. Later that day, Aang and Katara board an abandoned Fire Navy ship only to set off a booby trap, signaling to Prince Zuko, the banished prince of the Fire Nation and his uncle, Iroh, a retired general of the Fire Nation's Army, the whereabouts of Aang as well as Katara and Sokka's village. Upon returning to the village, Aang is banished by the suspicious Sokka, only to return and save the village from Zuko and his men. It is then that Aang, Katara, Sokka, and Appa set off for the North Pole and the Northern Water Tribe to find a waterbending master for both Katara and Aang to learn from.
In the third episode of the series, The Southern Air Temple, the group travels to Aang's previous home, which had been invaded by firebenders in their initial attack. Here, Aang learns the truth about his people as well as his mentor, Monk Gyatso. Also, he activates a shrine deep inside the temple, alerting the Fire Sages of his existence. Last, he finds Momo, the last remaining winged lemur. In the two-part episode, The Winter Solstice, Aang encounters his previous incarnation, Avatar Roku, for the first time and learns more about his quest. Not only must he master all four bending arts (waterbending, earthbending, firebending, and airbending) he must do so before next summer, when the return of Sozen's comet, a comet that grants firebenders extra power, will allow Fire Lord Ozai to finish the war.
In the sixteenth episode of the series, The Deserter, Aang and the others meet an ex-Fire Army general, Jeong Jeong while traveling through a part of the Earth Kingdom controlled by the Fire Nation. At first, Jeong Jeong refuses to teach Aang firebender, though he is a master, as it is not the proper cycle (Aang should master waterbending, then earthbending, then firebending), but changes his mind after a spiritual visit from Avatar Roku. Aang begins trainging, and is naturally gifted, mastering stances and breathing exercises extremely quickly. However, Aang soon becomes inpatient, pressuring Jeong Jeong to teach him real firebending, which ultimately leads to Katara becoming burned by Aang's carelessness. It should be noted that this is also how Katara learns of her inate ability to heal using water.
Finally reaching the North Pole in The Waterbending Master, Aang finds a Waterbending Master, Master Pakku. However, the master refuses to teach Katara because she is a girl. Aang initially decides to just teach Katara what he's learned during the day that night, but is quickly discovered by Master Pakku, losing his chance to learn waterbending from him as well. The next day, Aang apologizes, and Katara challenges Master Pakku to a battle after he still refuses to teach her, which she ulimately loses. During the fight, it is revealed that Katara's grandmother was Master Pakku's fiancee, who left him because of the Northern Tribe's sexist customs. With this realization, Master Pakku agrees to teach both Katara and Aang.
In the season finale, The Siege of the North, the Fire Nation attacks the North Pole under the command of Admiral Zhao. Aang realizes that the Water Tribe cannot defend against the fleet on their own, and seeks the help of the Ocean and Moon spirits in the Spirit World. Meanwhile Zuko, thought to be dead, infiltrates the North Pole and kidnaps Aang while he was under the meditative state. After a day of battle, Zhao reveals his plan for victory: he will capture and kill the Moon Spirit's mortal form - the source of all waterbending. Aang, learning of this plan, rushes back to the real world, where Katara finds him and rescues him from Zuko. They group arrived too late, and Zhao succeeds in killing the Moon Spirit. The Ocean Spirit, enraged by the murder, combines with Aang, and together they wipe out the remaining firebenders and drove off the invading fleet, as well as killing Admiral Zhao. Balance is finally restored, along with all the waterbenders' powers, when Princess Yue gives up her life to restore the Moon Spirit's.
Book Two: Earth
The Avatar State, the first episode of Season Two, begins with Aang and the group parting ways with a group of waterbenders led by Master Pakku who plan to help the South Pole rebuild. As they prepare to leave, Master Pakku gives Aang a box of waterbending scrolls and informs him that Katara will be his new master. Later, the group arrive at an Earth Kingdom base, where General Fong is supposed to escort them to Omashu. However, the general has his own agenda - to help Aang master his Avatar State. This ends in Fong's defeat after Aang does enter the Avatar State, after which Aang learns that if killed in such a state, the Avatar chain would be broken, meaning all of the Avatar spirits would die off.
Book Three: Fire
"The Awakening" opens a few weeks after the events of "The Crossroads of Destiny", when Aang wakes up with bandages, a scar on his back, a headful of hair, and the horrible knowledge that the world thinks the Avatar is dead. Angry and disappointed with himself for the fall of Ba Sing Se, he ran away from his friends with his glider in an attempt to finish his quest on his own. After getting caught up in the storm, he almost gave in to despair. It was only through the words of Avatar Roku and Yue the Moon Spirit to give him the encouragement that he can still save the world.
The rest of his friends managed to caught up with him in the Crescent Island, and with a new resolve, Aang decided that he should remain secret, and burned his prized staff, signaling his acceptance to leave the past behind.
The issue of how exactly they will wait out the time period until the invasion comes to rise, and Aang decides that blending in with the Fire Nation would be more suitable than hiding out. In addition to the increased safety, they would be able to obtain information on the Fire Lord. After obtaining sets of clothes, the group travel into a city. Aang hides his trademark tattoos through long sleeves and a waist sash tied around his forehead. There, Aang is captured by Fire Nation truant officers, and placed in school. When told to remove his headband, he persuades them to allow him to keep it by saying it covers embarrasing scars.
Aang finds a comfort in blending in and being normal, even making several friends and drawing the ire of a popular young man through his girlfriend's reaching out to Aang. Startled by the rigidness of the society, Aang and the group conduct a dance party, and are forced to leave the city.
The group continues to travel until reaching the isolated coastline where they are to meet the others for the invasion.
After reuniting with past friends from their adventures and talking over the invasion plans, Aang finally shaves his head, dons new Air Nomad robes and armed with a new glider that was a gift from Teo and the Mechanist. He was determined to find and fight the Fire Lord to end the war.
Aang is fun-loving, naive, and adventurous. As Michael Dante DiMartino, the show's co-creator said, "We wanted Aang to solve problems and defeat enemies with his wits as well as his powerful abilities." He possesses a deep respect for life and freedom; he does not eat meat and is often reluctant to fight. He craves the stimulation of new people and places; in short, he is the consummate tourist. His frequent off-course detours frustrate both allies and pursuers alike. This especially affects Sokka, who is constantly annoyed by Aang's unnecessary side-trips and distractions, which descends from Sokka's original suspicion of Aang in the first episode, which has still not completely died out. Yet Aang has always prided himself on a complex social network of friends extending over all four nations, and war will not stand in his way. In addition, he looks forward to playing with all the exotic fauna in each place he visits. Whether it's penguins, hog-monkeys or gigantic eels, no fit animal Aang sees goes un-ridden. Even the largest of predicaments does not seems to entirely rid him of his friendly and childish personality.
Aang feels a terrible guilt and burden in his duties as Avatar. Very much the reluctant hero, he wishes he had been there to help his people a century ago, but he had still rather live a child's carefree life. This initially caused him to conceal his true identity from friends, and he still has a tendency to slack off in his studies of the Bending Arts, even though he naturally excels at it.
Being the last Airbender and having no living peers (with the exception of the aged King Bumi and Guru Pathik), Aang cares deeply for those close to him, even to the point of deceiving and hurting others to keep the group together. In "Bato of the Water Tribe," Aang heard that Katara and Sokka might leave the group to visit their father, so Aang hid the map showing his whereabouts and lied about ever having it in the first place. In addition, Aang has shown various signs of being in love with Katara throughout the show, which became a problem to him later on, when he was instructed that he must detach himself from her to achieve the control of the Avatar State.
Events in the Earth Kingdom, however, have begun to take a toll on his care-free personality. Aang's attitude changed dramatically when Appa was captured. He became visibly enraged and hostile, particularly toward Toph, who was "keeping an eye on" Appa while they were gone. Despite attempts by Katara to calm Aang down, his anger continued to grow until finally he flew off to search for Appa alone. Eventually Aang returned to the group, but was still visibly upset. He violated the principles of Airbending when Momo was snatched up by a Buzzard-Wasp. He followed the creature and rescued Momo, but then unnecessarily struck it down with his staff. After this he returned to his friends to find they were saved by sandbenders. After Toph tells Aang that the sandbenders were the ones that stole Appa, he travels into the avatar state and destroys the sand gliders but yet he is stopped by Katara.
As he infiltrates the Fire Nation, Aang took delight of enjoying the brief life of an ordinary school kid in "The Headband", as well as involving in numerous scams in "The Runaway". However, by "Nightmares and Daydreams" Aang's fear and stress for the day he would fight Ozai manifested themselves when the gang would have to wait for four more days for the invasion, he also voiced his concern for his lack of knowledge on firebending, in which Sokka quickly assured him that he will not need it in the eclipse.
As the incarnation of the Avatar, Aang possesses the ability to bend all four elements. He is already an Airbending master and has made impressive progress with the other elements, except for Firebending, for which he has yet to find a master. Though he is able to master techniques with more ease than his young Waterbender friend Katara, his lack of focus has allowed her to surpass him. Now he must learn from her, as their teacher Master Pakku deemed her a master. He is an extremely skilled Waterbender, and in the episode "Bitter Work," Katara tells Aang he has the reflexes of a Waterbending Master. That being said, the gap between Katara and Aang in water bending ability appears to be getting narrower, as Katara continues to show great waterbending prowess, while Aang is rarely seen practicing and in battle he uses his earth and airbending more often.
The Earthbending style is the opposing style to his natural Airbending, and as such conflicts with his natural personality. At first, Aang's Earthbending abilities appeared stunted, as he has difficulty learning simple skills from Toph in Bitter Work as it was easier for Aang to simply avoid the obstacles physically. However, when he confronted with a need for direct opposition, rather than avoidance, he took his first step and successfully stood his ground to defend Sokka, who could not defend himself, and now Aang was able to assume the position of an Earthbender. By the time of "The Drill," his skills have improved dramatically, when he comfortably uses Earthbending in combat against Azula. He appears to have achieved mastery in Earthbending by the time of "The Tales of Ba Sing Se," creating a giant zoo with his bending, and by fending off hundreds of Earthbenders in "The Earth King". By the time of "The Runaway" he has at least begun learning how to see with earthbending like Toph does. Later, he incorporates his Airbender's staff into his Earthbending, much like Avatar Kyoshi incorporates her fans into her bending. It is possible for Aang to bend two elements at the same time, as demonstrated in "The Tales of Ba Sing Se." He has little skill with fire, but has received a rudimentary object lesson in breath control and Firebending. When he was briefly instructed by the fugitive Firebending master Jeong Jeong, he ignored warnings to restrain himself and accidentally burned Katara (leading inadvertently to the discovery of her healing powers). Newly respectful of fire's destructive power, he has not used Firebending since, and has even vowed to never firebend again, although, as Guru Pathik said in "The Guru," he will eventually have to, as he is the Avatar, therefore he is a Firebender.
As the Avatar, Aang is quite possibly the most powerful Bender in the world; he once used his Airbending skills to halt a massive lava flow without entering the Avatar State. It may be noted that his predecessor, Avatar Roku, had died attempting a similar feat. Additionally, Aang has exceptional natural talent towards all bending, performing Waterbending on his first try when Katara took several months to learn the same move, and assuming a perfect Earthbending stance on his first try. However, Aang is loathe to use his skills in battle, preferring to solve problems non-violently. Even when forced into combat, Aang typically holds back, fighting defensively and trying to subdue opponents without seriously hurting them, even if they are not human. This attitude was apparently common among Airbenders, who were all vegetarians and taught that all living things are precious.
The only exception to Aang's pacifism is when his friends are threatened; in which case, he gets very angry and relentlessly attacks his opponents, sometimes even entering the Avatar State.
In The Deserter, Jeong Jeong says that to master Firebending, Aang, as the Avatar, will need to first master the other Bending Arts in order and not to deviate from their natural order--Air, Water, Earth, and Fire--hinting that the disciplines of one Bending Art will support the disciplines of the next Bending Art in order--'evade and avoid' - 'redirect and turn against the opponent' - 'standing one's ground and enduring' and 'pre-emptive first strike'. In Bitter Work, Iroh comments "It is important to draw wisdom from many different places. If we take it from only one place, it becomes rigid and stale. Understanding others, the other elements, and the other nations will help you become whole...It is the combination of the four elements in one person that makes the Avatar so powerful," as he reveals how a Waterbender's technique of redirecting energy enabled him to develop his own technique to redirect a bolt of lightning--proving that the disciplines and principles of one Bending Art support the disciplines and principles of another Bending Art. Other than his brief training with Jeong Jeong, Aang is yet to begin Firebending. During the same episode, Jeong Jeong said in a brief exchanging of words with Admiral Zhao that "I have never seen such raw power", a reference to Aang's bending prowess.
Aang is the newest incarnation of the spirit of the planet, which has been continually reincarnated since time immemorial. The passage of reincarnation moves from the population of the Air nation to the Water, Earth and Fire nations in order. The most recent incarnations were Avatar Roku (fire), Avatar Kyoshi (earth), Avatar Kuruk (water) and Avatar Yangchen (air).   Aang often receives advice and guidance from Avatar Roku, the previous Avatar incarnation. Born into the Fire Nation in life, Roku is a benign force in spirit, serving as Aang's advisor and protector. On the Winter Solstice, after informing Aang of the impending return of Sozin's Comet, he manifested himself to defeat a group of Firebenders holding Aang's friends hostage. (When Roku manifests, his voice can be heard behind Aang's when he speaks.) He has guided Aang several times since, appearing to Jeong Jeong to persuade him to teach Aang, offering critical wisdom in the ways of the Spirit World during "The Siege of the North", and most importantly, revealing to Aang the nature of the Avatar State. Roku recently revealed to Aang his past relationship with Fire lord Sozin as was explained in The Avatar and the Fire Lord. This was so that Aang could have an understanding of how the war began so that he could decide how to end it.
After receiving a letter from Guru Pathik in "The Earth King", Aang journeys to the Eastern Air Temple to learn to control the Avatar State. Guru Pathik reveals that the secret of entering, controlling, and leaving the Avatar State by free will lay in the 'releasing' of seven chakras. Aang has little trouble with the first six, but struggles with the seventh - earthly attachments, namely, love. Aang's love for Katara, accompanied by a vision of her in dire need of help, captured in Ba Sing Se, causes him to leave the Guru and return to Ba Sing Se. Guru Pathik states that Aang's refusal to let Katara go has 'locked the final chakra' and disallowed him to enter the Avatar State at all. Later, in "The Crossroads of Destiny", however, Aang begins to open the Seventh Chakra and enter the Avatar State by doing just as he had been told - letting go of his attachment to Katara. However, moments after entering the Avatar State, the process is interrupted as he is struck with lightning from behind by Azula, killing him and removing him from the State. Fortunately, after their escape, Katara is able to use the water from the spirit oasis to resurrect him.