Clowns are the guys that you supposedly loved when you are a child.
Picture a towering figure with a white face and bright red hair, wearing puffy pants and silly floppy shoes. This impossing figure is trying to make you laugh, usually through slapstick comedy.
They are everything your parents warned you about when they told you about Strangers. They have gifts of baloons, sometimes animals, and they want you to come closer. See IT and Pennywise the Dancing Clown for further details.