All they do is play a version of themselves over and over and over again and they are paid the big bucks because most people love to see those specific characters on screen. An actor on the other hand, seeks a wide range of roles and parts, is perfectly happy being in a supporting role, and has actual real interest in acting as an art and craft.

Michael Caine had a fantastic quote about that subject:
“The difference between a movie star and a movie actor is a movie star gets a script — movie star Michael Caine gets a script and he says, “Now how can I change this script. It’s not quite Michael Caine. I’ve got to change it.” And they say things like, “Michael Caine wouldn’t wear that kind of thing. Michael Caine wouldn’t say that to a girl. Michael Caine wouldn’t drive that sort of car. So we’ll have to edit the script.” And everyone says, “Oh, of course, Michael, we’ll change all that.” They change the script to suit them. A movie actor, he changes himself to suit the script. He wears glasses, puts on a fat belly, gains weight, loses weight, grows a beard, moustache, any bloody thing.”