The vast majority of the computers (at this moment) have one single monitor on which one single (electronic) desktop is visible - and this space can easily become crowded by all the programs, applications and windows that people need to use - a Virtual Desktop Manager is a program that will provide you with multiple desktops by "virtualizing" the normal desktop, and as a result each of those virtual desktops will be better organized and more productive than the original (single) one! (and actually in certain conditions a good virtual desktop manager can be more effective than multiple monitors!)
Not all Virtual Desktop Managers are created equal, and the features and stability of the programs currently available can be very different - most programs will only have a minimal set of features that are only suited for learning more about virtual desktops, a few other programs implement a number of functions that usually can help "managing" the extra desktop space - and from this last group very few can also have very good stability, flexibility and support!
If you want to learn more about Virtual Desktop Managers this small guide (or comparative review) will try to help you, but (unlike some sites that claim to have independent reviews but are only "web decoys" for some of our competitors) we will not claim total impartiality (after all, the real experience can only be gained by using a product continuously, and we are doing that with all our products and not with the products from our competitors), nor will we present all the bugs and problems from other programs (unless our competitors will pay us to discover / document things, we see no reason to give away our battery of tests :)
There are operating systems where some Virtual Desktop Managers are implemented inside the operating system (like BeOS) or inside the "windowing system" (like in Linux/FreeBSD/OpenBSD and similar, where some windows managers under XWindows can implement more than decent features!)
