Difference between actor and pawn

Hello.

Im a former unity developer who rencently ported to unreal 4. Im therefore having a hard time grasping what the different things do and dont. One thing i dont understand is the difference between actors and pawns. To me it seems that actors server the same purpouse as gameObjects do in unity. But i dont know what the pawns do. Could anyone give me some concrete info on what they do and dont?

Thank you.

Extra note. If anyone could tell me what characters do too i would be very grateful