Virtualization is hot right now. I sale VM Ware products. I'm currently studying for the VM Ware professional sales. There are plenty of other player in the field right now. There are open source solutions. Such as Virtual Box.
There is also Novell is Xensource.
Virtualization allows you to run multiple virtual machines on one computer or server. It is handy. I run Parallels here at home on my Macbook. The benefit is that I can run Mac OS X and then have Redhat Linux in another window. This allows me to focus on programming in Linux and using Mac OS X for my photos or running ITunes.
Companies can use virtualization to reduce IT cost's, There does not have to be as many desktops. You can run multiple virtual machines on the server and have clients connect with dumb terminals.
Virtualization is also good for security. A virus or worm will only stay in the virtual machine and not infect other machines, or virtual machines. Virtual machines can also be transported with VMware. This can be carried on person in a USB drive.