Sounds as if a window manager is just like any other program, just that it only fills the unused screenspace with a few buttons, clock, background, taskbar and then translates your key/mouse input a bit and sends it back to X but doesnt even communicate directly to the other running programs? All that buzz about people loving/hating these things made me think there must be something more to it, but I couldnt think of anything.
Well, it manages all of the screen space, but yeah that's the gist of it. Personally, I do most of my work in terminals so I used a tiling window manager called 'awesome' which makes it easier to organize multiple terminals and navigate with the keyboard.
-Josh