Aang is the main character in the cartoon Avatar: The Last Airbender.
In Avatar, there are four nations: The Air Nomads, the Water Tribes, the Earth Kingdom, and the Fire Nation. Some people are benders of their respective element(air for Air Nomads, water for Water Tribes, etc.), although most people lack the ability to bend. Bending is essentially being able to manipulate whatever element it is. As Aang is an airbender, he can control air.
The Avatar Edit
Aang is more than an ordinary bender. He's the Avatar. When the current Avatar dies, they will be reincarnated into the nation next in the cycle. The cycle's order is water, earth, fire, air. So when Aang died, Korra was born into the Water Tribe as the Avatar. The Avatar is exceptional at bending their own element, and also is the only person who can bend all of the other elements. Their potential for mastery of the other elements may vary, although it always seems to be better than any natural bender of that element. One character says that it has to do with what your native element is, and another says that it has to do with your personality. The Avatar can also go into the avatar state, where his bending abilities are increased by a whole lot, but if the avatar is killed while in the avatar state, they don't reincarnate. It's activated automatically in times of extreme danger or strong emotion, until the avatar in question has cleared their chakras, at which point they gain the ability to activate the avatar state at will, as well as keep from entering the avatar state when they don't want to. Aang does this in season 2 episode 20. However, learning to maintain control during the avatar state, and learning to not collapse immediately after, are skills that are only learned with practice. Aang doesn't learn these things until long after the original show has ended.
Aang has a quarterstaff that he uses as a weapon to supplement his airbending. It can also turn into a glider, but he has to use his airbending to actually glide with it. Eventually he loses it, and someone makes him a new one. It's made out of metal instead of wood, and it has a nut dispenser.