Compiz and Compiz Fusion are merging and are now known as Compiz.
Compiz is a compositing window manager. It has a flexible plugin interface which allows developers to use it for many different tasks.
Compiz Fusion is the result of a merge between the well-known Beryl composite window manager and Compiz Extras, a community set of improvements to the Compiz composite window manager. Compiz Fusion aims to provide an easy and fun-to-use windowed environment, allowing use of the graphics hardware to render each individual window and the entire screen, to provide some impressive effects, speed and usefulness.
