Working with Virtual Desktops in Ubuntu

Windows works on the premise of everything taking place on top of a single desktop. When you start a new program, it runs on top of the desktop, effectively covering up the desktop. In fact, all programs are run on this desktop, so it can get a bit confusing when you have more than a couple of programs running at the same time. Which Microsoft Word window contains the document you're working on, rather than the one you've opened to take notes from? Where is that My Computer window you were using to copy files?