Aang, a 12-year-old Airbender of the Air Nomads' Southern Air Temple, learned from the elder monks that he was the Avatar. The Avatar is the master of all elements: earth, fire, water, and air. Usually, the Avatar is told of his or her true identity after turning sixteen; however, the monks feared that a war between the four nations was on the horizon and that soon the Avatar would be required to maintain balance and order in the world.
Aang is frozen, and he ends up being un frozen 100 years later after the fire nation has taken over. Aang is trying to master all the elements and bring peace to the world.