The Legend of Korra’s fourth and final season, Book 4: Balance, returns this Friday! You’ll be able to watch here. Trying to catch up with all three seasons in one day is a pretty tall order, but luckily the weekend will soon be here! The first three books (as seasons are called Avatar: The Last Airbender and Legend of Korra) are available streaming on Nick.com.
Avatar: the Last Airbender follows Aang, the last airbender, who survived the Air Nomad genocide from the Fire Nation. Together with his friends Sokka, Katara and Zuko, Aang fights to prevent the Fire Nation from taking over the whole world, all the while mastering all four elements.
The Legend of Korra is the direct sequel to Avatar: the Last Airbender, taking place 80 years after the end of ALTA. Korra, upon discovering she was the avatar at the age of four, was placed under the direct care of the Order of the White Lotus and learned to water-, fire-, and earthbending. Korra sneaks away from the Order of the White Lotus compound to learn airbending from Tenzin, the son of Avatar Aang, in Republic City.
Elements: Air, Water, Earth, and Fire.
Bending: The ability to control one of the aforementioned elements, i.e. waterbending. A person who bends an element is known as a bender.
Avatar: one person who has the ability to control all four elements. The avatar is born into one of the four nations and learns to bend the four elements. The Avatar is supposed to help maintain balance between the Four Nations and the spirits.