Bending, the ability to manipulate an element, is very significant to all aspects of life in the World of Avatar. There are five known bending arts; four of them bend a specific physical element, while the fifth bends the energy within the human body itself. The four elemental bending arts are based on the four classical elements; water, earth, fire, and air, and each are manipulated through certain martial art styles which are reminiscent of the qualities of the element itself.
The fifth bending art, energybending, is unlike the other four in that very little physical action is required to direct the bending itself. The four elemental bending arts are all dependent on the energy, or chi, within the human body, relying on its flow through the body to manipulate a specific element. Energybending, on the other hand, is concerned with the manipulation of the energy itself and is able to remove one's bending abilities. The symbols of the four bending arts as drawn by Iroh. Each element is also associated with a particular nation in the world; the Water Tribe, the Earth Kingdom, the Fire Nation, and the Air Nomads, though other bending affiliated groups exist (e.g. the Sun Warriors, the Foggy Swamp Tribe). Though each nation is affiliated to a specific bending art, not all from any nation, with the exception of the Air Nomads, are born with the ability to bend. It is unclear how the ability to bend is distributed amongst the population or how closely it is linked to heredity; even among identical twins it is possible for one to be a bender and the other not. In the case of mixed marriages, the children may be benders of either element if they are benders at all; for example, firebender Mako and earthbender Bolin are brothers with parents from the Fire Nation and the Earth Kingdom. The only case of any one person being able to bend multiple elements, or an element not associated to their nation of birth, is the Avatar, the spirit of the world incarnate, having the ability to practice all five bending arts