You remember Avatar: the Last Airbender, right? Sure you do.
If you haven't managed to see it, it combined a fascinating new world, compelling characters, great animation and a complex story involving martial artists who huck huge amounts of elements at each other. What's not to like? Go watch it immediately.
Then a live-action movie came out. It was awful. Seriously. You're better off not asking about it.
The only plus side to the movie is that Nickelodeon decided to give the original creators of the show the chance to do a sequel series, with a bigger budget no less. And so The Legend of Korra was born.
Set 70-odd years after the events of the first series, the new show focuses on Korra, the new Avatar after Aang. A native waterbender, Korra quickly mastered earthbending and firebending, though airbending eludes her. Probably because the spiritually-focused discipline clashes with her brash, impatient personality. She also has a huge polar bear dog named Naga.
To learn airbending, she travels to Republic City, a thriving metropolis founded by Aang and Zuko after the events of the first show. It's technologically advanced -- think 1920s Hong Kong -- and a utopia for all four kinds of benders and non-benders alike. Er, that's the theory, anyway.
Her airbending teacher is Tenzin, one of Aang's sons. He's patient, focused and voiced by the awesome J.K. Simmons. His kids are Jinora, Ikki and Meelo, who are... well, less patient and focused.
Along the way, Korra meets Mako and Bolin, brothers who compete in pro-bending. Mako, a firebender, is stoic and reserved, while Bolin, an earthbender, is goofy and excitable. Together with Korra, they compete as the Fire Ferrets, possibly named after Pabu, Bolin's fire ferret.
Lin Beifong is Toph's daughter, only she's less blind and more of a hardass. She leads Republic City's police force, who are metalbenders to the man.
Asami Sato, heir to motor company Future Industries, joins Team Avatar mid-way through book one. She's not a bender, though she's still formidable in combat with her electrified gloves.
Remember how I said Republic City might not be the utopia its creators hoped for? Here's one of the reasons. Amon was the mysterious and charismatic head of the Equalists, a group dedicated to opposing benders of all type, since the Equalists feel their massive power oppresses non-benders. And he had the means to do it too -- not only did he have a large force of chi blockers, who can temporarily block bending, and an array of high technology at his disposal, Amon had the ability to take a person's bending away. Permanently.
Without getting into spoilers, Book One ended with Amon neutralized and Korra in touch with her airbending side. What's next for her? Starting in September, you can find out in Book Two: Spirits.
After that we'll get two more seasons, but no information has been released yet.