Compiz is an OpenGL compositing manager, which means that it enhances
the overall user interaction by adding fancy effects to your windows,
from drop shadows to desktop effects like the Desktop Cube or the Expo view.

Compiz can also be a window manager, which means that it is the software
between you and your desktop apps. It enables you to move or resize windows,
to switch workspaces, to switch windows easily (using alt-tab or so), and so on.