Virtualisation technology is becoming increasingly popular in the design of network infrastructure.
Servers architecture are designed to only allow them to run only one operating system at a time.
On average a single operating system would use less than 15% of the servers full capacity with the rest of the servers resource not being used whereby the server is not being used to its maximum potential.
Virtualisation gives the ability to install a hypervisor (VMWARE or Microsoft Hyper-v) whereby you can then install multiple operating systems as virtual machines that would run on the single physical server.
The hypervisor manages the systems hardware resources so they are distributed efficiently among the virtual machines.
Vitualisation allows the physical server to utilise 80% of its full capacity.