Okay...I'm scanning through my string theory text and I've got a problem. I'm trying to understand some notation; specifically groups of the form Spin(4, 1) (and similar groups.) I took a look at a Wikipedia article but it referred to Clifford Algebras and I'm not experienced enough to understand the construction. Does anyone have a "simple" description of the "Spin" system of groups? I can add more details as necessary.