Virtualization is the art and science of replacing many small physical servers by a larger Physical server running in virtual mode. VIrtualization will increase the utilization of costly hardware resources such as CPU, memory and hard drive. Hardware is consolidated and a new virtual machine can be created as needed without the need for an up-front hardware purchase. A large server can host many guest virtual machines.
A virtual machine server can be easily setup, configured and controlled from outside than a physical one. It is far more flexible and easier to control. Any error inside a virtual machine server will not damage the host server. Therefore a virus attack on a single virtual server will not affect the host or other virtual servers. Finally, a virtual machine can be easily transferred from one server to another server with minimal effort.