The Legend of Korra follows Korra, who is an Avatar. This means that she has a lot of responsibilities—keeping peace on earth, saving the world, keeping the spiritual world and the physical world connected, etc. Frankly, it's a lot. Fortunately, Korra just has to master the bending of air, and she'll have all four elements under her belt. Unfortunately, she doesn't get along with Tenzin, her airbending teacher.