Chewbacca is a 200 yeard old wookie from Kashyyyk. For those who didn't know, he has a wife that he sees a few times a year, but to wookies, a life debt is more important. Chewie became an Imperial slave when the Empire took over Kashyyyk. He was later freed by a young Imperial pilot named Han Solo. For this, Chewie owed a life debt to Solo. So the two of them went around doing smuggling operations until they met Luke Skywalker. Then Chewie joined Solo and Skywalker when they joined the rebellion.
Chewie is a surprisingly good mechanic for a two meter tall furball. Wookies take life debts very seriously. When Han married Leia Organa, the life debt was extended to protect her and her brother Luke. The wookie has been on many adventures all over the galaxy and is a true hero.