Who is Arya Stark from A Clash of Kings and what is their importance?

Arya Stark is the daughter of Catelyn and Eddard Stark, and sister of Sansa, Robb, Bran, and Rickon Stark. She escapes from King's Landing with Yoren after her father's execution. When several members of the city watch stop the group, they say they want Gendry to take back to King's Landing, but they don't reveal why. Yoren runs off the goldcloaks and the party flees to Harrentown, where they are attacked by Ser Amory's men. Arya helps the other children escape through a trapdoor in the barn. Three convicts are trapped in a wagon, including Jaqen H'ghar, and Arya gives him an ax so they can get free.