What is Satanism really about?

First, i am not interested in becoming a satanist.. no offense! I'm just wondering, I heard most lean more towards self worship as opposed to worshiping satan as an entity (living being). Is this true? Are there different "branches", (basically different versions of satanism)? I just want to be informed so if satanism ever comes up I don't talk about it and get it all wrong and sound like an ignorant bigot.