Fourteen years old and the only Waterbender in the whole South Pole; Katara had to grow up rather quickly which made her very mature for her age. Her mother was killed in a Fire Nation attack when she was 8, and her father left to fight in the war when she was 12. Raised in a small village in the South Pole with her older brother Sokka, after their father left they were mostly taken care of by their grandmother, Gran Gran. While Sokka was off "playing solider", Katara was cooking, cleaning, and doing the laundry. Things haven't been easy, but she never lost hope that it would get better -- that the Avatar would return. It must be fate that she and her brother were the ones to discover Aang frozen in an iceberg during one of their fishing trips gone awry.
Trusting of Aang from the moment they meet, Katara has constantly defended him from angry accusations, misunderstandings, and etc. She's very protective of him, and is always there to give support and a helping hand when he needs it. She also has a lot of faith in his abilities as the Avatar. While it's obvious that she cares for Aang, it's not quite clear if she has a crush on him like he has for her. Many of Katara's responses towards him feels almost motherly (in my opinion), but I'm sure that as time goes by their relationship will become deeper.
In episode 6, while helping an Earth Kingdom mining town rebel against the occupying Fire Nation, Katara lost her necklace. It was found by Prince Zuko, and later in episode 9 he used it as leverage to get her to tell him where Aang was. She refused to tell him though, and later escaped. The necklace was again brought to light in episode 15, where Zuko used the necklace to help Jun and her Shirshu track Katara and co. But during a fight, Aang managed to steal the necklace back from Zuko, and returned it to Katara, earning him a kiss on the cheek.
In episode 16, Katara learned that she had the ability to create healing water after Aang accidentally burned her hands while firebending. According to Jeong Jeong, the ability to heal is rare and found only among great Waterbenders.
Katara is caring, usually responsible, and protective of the downtrodden. She's also mature, wise beyond her years, and is a fighter at heart. When she sees a wrong being committed, she won't hesitate to try set it right. She wears a necklace that once belonged to her mother, and it gives her strength and courage for when the road gets tough. She believes in the Avatar lore and dreams of mastering her Waterbending skills. She travels with Aang and Sokka on their journey to prepare Aang to save the world. More often than not, Katara is the voice of reason in the group. That, however, doesn't make her immune to making stupid mistakes, or bad judgement calls because of cute boys.