yep...lets you run an OS in a window, as if it were a separate computer.
So...you get a beefy enough computer, you could have WinXP running on your computer, then have DOS in a window, red hat in a window, Windows Server 2003 in another Window, etc etc...and populate your network with numerous boxes, all of which are virtual.
The major benefits are:
a. You can run dos, which can let you run dos games or applications
b. You can run Linux to play around in without having to dedicate 3+ hard drive partitions to it, but you can run Windows and Linux apps at the same time on the same pc without having to deal with WINE.
c. You can play networked games with yourself.
