The word "Virtualization" on its own, is too wide to discuss. But to cut it short, its a process of making one thing look like another. For our purposes we are referring to the ability of a computer to be split into multiple parts where the parts are (relatively) indistinguishable from the whole. For example, running different Linux environment on a single machine. Virtualization is often posed as a tool to over ride accustomed practice to having dedicated environments for each application, due to this one application per server deployment model, the majority of systems are grossly under-utilised like CPU utilization below 10% is normal. By virtualizing the physical hardware so that many “servers” can run simultaneously on the same physical machine we can drive utilisation much higher, to 50% or more. Hope it help!
Cisco Switch and Router Configuration