Satan is a title. It is most commonly associated with Lucifer Morningstar, classically depicted as "The Devil" in most Judeo-Christian lore. The term Satan is actually a title, referring to the ultimate ruler of Hell. However, it is often mistaken as a proper name. The practice of worshiping the devil is called Satanism.
Yeah... the big red gay guy that hangs out with Saddam Hussein on South Park is Satan.