Aang, a 12 year old Air Nomad, never wanted to be the Avatar. He just wanted to be a kid who could have a lot of fun. But when you find out that you're the legendary Avatar, nothing stays the same. Though technically he was suppose to have been told of his fate when he turned 16, the five monks of the Southern Air Temple told him early because they feared war was on the horizon. Aang reluctantly accepted, for a while anyway.
But a conflict of interest between the monks resulted in Aang being transferred to the Eastern Air Temple to separate him from his caring guardian, Monk Gyatso. However this was the last straw for Aang, and so one night before he was moved he ran away with Appa, his flying bison. They got caught in a horrible storm and were thrown into the ocean. Their only means of survival was for Aang to encase them both inside a large air pocket, which eventually froze over and became an iceberg. They stayed trapped inside for 100 years, until Katara and Sokka discovered and freed him. He became fast friends with Katara, but it took more effort until Sokka began to trust him. Naturally, Aang remained the same as he was when he was last awake 100 years prior, but his outlook begins to dampen as he adjusts to just how much the world has changed without him. While he was frozen a bloody war between the Fire Nation and the other nations broke out,
which is still being waged when he awakens. You can see his attitude slowly begin to change as he sees more of the destruction from the war, and all the people who've suffered because he wasn't there to prevent it.
Traveling with his now good friends Katara and Sokka, along with pets Appa and Momo, Aang is exploring the world in hopes to finish his training and truly become the Avatar. In order to do so, Aang must master Waterbending, Earthbending, and Firebending, along with furthering his Airbending skills. Although because the Avatar is considered a 'great bridge between the natural and spirit worlds', he also has to learn about being the Avatar and using the unique powers that come with that title. Only when he has finished his training and is truly ready will he stand a chance of returning peace to the world and stopping Fire Lord Ozai. But unfortunately for Aang and the other nations, a comet will pass by the world near Summer's end, which will empower Ozai and the other firebenders to unfanthomable levels. Aang better hurry!
Before the iceberg incident, Aang trained at the Southern Air Temple and was raised by monks along with a handful of other airbending boys. He was the pupil of Monk Gyatso, master Airbender and a kind fatherly-like teacher. After Aang was told that he was the Avatar, the other boys basically excluded him, so Gyatso became his only real friend there. In the Earth Kingdom city of Omashu, Aang had a friend named Bumi who taught him to always keep his brain open to the possibilities, which is great advice. Aang also had a friend in the Fire Nation, a boy named Kuzon, with whom they always got in and out of trouble.
Aang is energetic, a vegetarian, and loves animals and riding them. He feels horribly guilty almost every time he comes across a place that was destroyed because the Avatar wasn't there to save them; and is always looking for adventure despite his duties as an Avatar-in-training. He's the only known Airbender left in the world as the Fire Nation apparently killed all of the others, and currently knows Airbending and some Waterbending and Firebending. He first learned how to waterbend thanks to Katara, and had training from Jeong Jeong that led him to learn firebending. But because of an accident that burned Katara's hands, Aang is very apprehensive about using his firebending skills.
When Aang's life is threatened, he is able to call upon his Avatar spirit and use the Bending Art that best fits the situation. But doing so requires a lot of energy, and Aang usually collapses afterwards leaving him open for attacks. Good thing he has Katara and Sokka to back him up. Aang has a flying bison named Appa and a winged-lemur named Momo, and together they represent all that is left of the Air Nomads. Aang also has a pretty-big crush on Katara.