“VirtualBox is a general-purpose full virtualizer for x86 hardware, targeted at server,
desktop and embedded use.”
VirtualBox is just a virtual machine running on top of any operating system. Therefore
you can run another operating system on top of your current operating system. It
is quite quick to use, and is widely used so it has a number of tutorials to get
started. You can use an operating system on CD or a downloaded version on VirtualBox.
It will only be a good virtual machine on top of your operating system as long as
you have a high-end PC. If you don’t, the system will be so laggy that it may not
be worth downloading it.
It is not the best in terms of stability, i.e. a high end PC is required yet again.
It lets you run an operating system on top of another one!