I never was a Windows user and there is something I just cannot understand: once you have your word processor, your web browser, your email application, your instant messenger software and some windows open to explore your files, how do Windows users manage not to get lost in this clutter?
Workspaces is a feature I would never trade for anything else. You probably only have one screen, right? Try Linux, and you have four. Well, you can't actually look at the four of them at the same time, but this doesn't matter since your eyes can't look in two directions at once, right? On the first screen, lets put your word processor. On the second one, your instant messenger software. On the third one, your web browser. So when you're writing something in your word processor and you want to check out something on the web, no need to review all your windows to find your browser, stacked all the way behind the others. You just switch to your third screen and voilà, here it is.
Take a look at the following screen, and pay particular attention to the bottom right of the screen:
That's your "workspace switcher". You can see it has four (virtual) screens, but you can have more than this (I use 12 of them, but some people have many more). The one on the left is highlighted: it's the current one. To switch to another one, just click on the one you want (each one of them shows a small preview of the windows they contain: in this case the three others are empty), or use a keyboard shortcut.