Avatar Aang, an Air Nomad, is the current Avatar, the manifestation of the world in human form, and thus the only person in the Avatar world who can use all four bending disciplines: Airbending, Waterbending, Earthbending and Firebending. He is also one of the few Avatars to use Energybending, and the only one to use it during the series.Before the beginning of the series, Aang was frozen in an iceberg for 100 years.
He emerges, still biologically twelve years old, into a world engulfed by war. During his absence, the Fire Nation waged war with the other nations, and managed to completely wipe out the Air Nomads. It falls to Aang, the last of his kind, to put a stop to the war by mastering the other three elements and defeating Fire Lord Ozai. He remains something of a goofy, kind kid at heart, despite the overwhelming loss of his people and the heavy burdens with which he has been given.In his childhood, Aang lived at the Southern Air Temple, with a father figure in Monk Gyatso. While still a young boy, he unconsciously showed himself to be the Avatar when he chose the Avatar Relics to play with. Due to the signs of a possible war, Aang was told about his status as the Avatar at age 12, four years earlier than the usual.
Aang felt burdened by his status, and came to spend more time practising Airbending with the monks than playing with his friends, as he was used to. After learning that he'd be sent to the Eastern Air Temple in order to complete his airbending training away from Monk Gyatso, who other monks thought to be too soft on Aang, he attempted to run away on his flying bison, Appa. Shortly after running away, Aang and Appa were caught in a storm, crashing in the water and being swallowed by the waves. Aang saved himself and Appa unconsciously by entering the Avatar State, freezing the two in a block of ice.
And now, as The Last Airbender, Avatar Aang must save the world...