Some of those you named are "Window Managers" and others are "Desktop Environments." This article should give you a basic understanding.
They both do basically the same thing... give you a working graphical desktop. The Window Managers are usually more simple, use less of your RAM memory, and may seem to be a bit quicker or more responsive when opening up programs. The Desktop Environments are more complex, use more of your RAM, and sometimes may feel a bit slow or sluggish. But the DE's are usually a bit prettier, and more people use them than the WM's.