In computing, Virtualization may refer to many things but we will discuss most compelling topic today. The Hardware Virtualization.

In terms of Hardware, Virtualization refers to a technique by which a single Server/PC can be converted into multiple pc's/virtual pc's inside the main physical pc.
It means a single hardware but virtually acting as multiple hardwares.

Physical Machine:
The Computer that you can actually physically interact with.

Virtual Machine (VM):
Virtual Machine is a pc inside that original physical PC that acts completely (or less) as the complete physical machine.
There are many names of Virtual machines, some are.
Virtual PC
Virtual Private Server (VPS)
Virtual Dedicated Server (VDS)

That small article suggests what actually virtualization is, stay tuned with adminspoint to get know more about virtualization.