Exposé is a window-clutter-management feature of OS X 10.3 Panther.
With one keystroke, you can 1) Show all open windows and select one, 2) Show all the open windows in the current application and select one, 3) Push everything aside and view the desktop. The default keys are F9, F10, F11 respectively, but they can be changed at System Preferences | Exposé.
This is the coolest thing in interface design since the mouse, and as Archicad users, it's extra-cool for us.
Come to think of it, I do have a lot of windows open.