Mimi, are you reading something to do with sports? That's the typical connotation for "All Star" because in many professional sports in the U.S., there is a mid-season game featuring the best players from each team, which is referred to as the "All-Star" game, hence the players are on the "All Star" team and are called "All Stars" for short. This term is sometimes used in other settings as well, but I believe the origin is sports. Does that help?
Elizabeth
