Before virtualization became publicly available, the idea of one application per server resulted in server sprawl.
A hypervisor is software between the physical hardware and the virtual machines.
A virtual machine is flexible, as its physical form is a set of files, configuration file, and virtual disk files.
Virtualization of IT resources makes cloud computing, as we know it, possible; it includes server virtualization, storage virtualization, and network virtualization.
Storage virtualization abstracts the physical resources, and a logical representation of them is presented to virtual machines by the hypervisor
Virtual machines can be set up with virtual Network Interface Cards (NICs), which connect to virtual switches, creating a virtual network.
Virtualization is the abstraction of computing resources from the physical hardware, making it possible to run several operating systems on one computer.