Aang is a young Airbender born to be the “Avatar” A being granted with the gift to control all four elements (Air, Earth, Fire, and Water) in order to have the power to enforce balance between all four nations which are named after the four elements. The Avatar is born on earth as a regular human being so that he/she can go through the same difficulties and challenges as anyone else, allowing him/her to deal justly and with empathy towards the nations for which The Avatar is responsible to care for.

Aang is a young Airbender, with the heavy responsibility restoring peace as the Avatar thrust upon him.
Aang is a carefree happy individual who goes through several intense challenges throughout the show, later on he masters the “Avatar State” and all four elements, Water, Earth, Fire, and Air. This allows Aang to end a century long war and bring peace once again to the four nations.