Princess Azula is Zuko's younger sister and is the favored child of Fire Lord Ozai. She is named after her grandfather Azulon, and was considered to be born lucky. She is a Firebending prodigy with powers on par with her father, and has the ability to create and guide powerful lightning attacks. She attended the Royal Fire Academy for Girls, and has been childhood friends with Ty Lee and Mai. She has always been loyal to Ozai, and thinks very little of her uncle Iroh. Growing up, she was often reprimanded by her mother Ursa for the mean and/or disrespectful things that she said.
Azula is manipulative, cold-hearted, vicious and a perfectionist. She is usually calm and in control when with others, but can become enraged instantly. She is the type who will get her way, no matter what. She enjoys seeing others suffer, especially her brother Zuko.
At the end of season one, Fire Lord Ozai gave Azula the task of arresting Zuko and Iroh (who by this time are considered failures/traitors) and bring them back to the Fire Nation. She traveled to the Earth Kingdom in an ornate battle ship with a small army of Firebenders and twin elderly women who may be Azula's instructors. Three weeks or so later (where season two begins), Azula and her entourage track down Zuko and Iroh. She convinced Zuko that their father regretted his banishment, and that Ozai wanted him to come home. Despite Iroh's skepticism, everything was going according to plan until Azula's captain called Zuko and Iroh "prisoners" while they were boarding her ship. >_<; Zuko and Iroh escaped, Azula's captain vanished, and the hunt was back on.
It was soon decided between Azula and the twin elderly women that if Azula was to keep the element of surprise while tracking Zuko and Iroh, she would need to leave the royal procession behind and form a small elite team. She chose her friends from her days at the Fire Academy: Ty Lee, a nimble, free-spirited girl who can attack the body's pressure points that stop it from element bending; and Mai, a dreary, impassive girl who is skilled at throwing blades. Not too long after their reunion, they battle Aang, Katara, and Sokka after a hostage trade fails. The trio escapes, and Azula adds the Avatar to their list of targets.
They have continued to track down the Avatar's group and her fugitive family, using transportation like a mechanical bulldozer/bullet train thing, and giant lizard creatures that can walk on water.