What Is a Virtual Machine?
Available using solutions such as VMware, Virtual PC and VirtualBox, a virtual machine (or VM) is a software environment that emulates a hardware computer system, making use of the physical hardware resources on your computer to do so, such as memory, the CPU and hard disk space.
Virtual PC is more suited to VMs running versions of Windows, while VirtualBox is an open source solution commonly used on Linux computers (although Windows and Mac versions are available).
Most popular for any sort of advanced virtual machine task, however, are VMware Player and VMware Workstation, two excellent tools that can be used to create and run a virtual machine on your computer. They’re particularly adept at handling VMs that feature previous releases of Mac OS X such as Snow Leopard, and following the release of Lion more and more people are using the new Mac OS X release as a virtual machine on their Windows computer (or even on their Mac or Linux computer).
Virtual machine files are cross platform, as a result these VMs can be used on any device which runs a suitable application.