Energybending originates before the Avatar, the four nations and the four main bending elements. It is the power to bend one’s life energy. In the time, before the Avatar, the elements were not yet divided and people bended energy within themselves. The people of the world left Energybending behind, after discovering the four elements. The ancient lion turtle was the last known guardian of the art and passed it down to Avatar Aang. Aang utilized Energybending to take away Fire Lord Ozai’s ability to Firebend forever.
28 years later, Aang used the art of Energybending to remove Yakone’s ability to Waterbend. After the Anti-Equalist Revolt, the spirit of Aang restored Korra’s bending abilities and bestowed the ability to Energybend to her, as well. Korra used her new ability to restore the bending lost by the victims of Amon.
Energybending can do three things: take away one’s ability to bend, transfer knowledge or restore one’s bending abilities. Unlike the other bending elements, Energybending is incredibly dangerous to bend as it has the possibility - if one is even somewhat weak or bendable - to corrupt or destroy the bender.
In the era before the Avatar, we bent not the elements but the energy within ourselves.