A hypervisor can run on bare hardware ( Type 1 or native VM) or on top of an operating system ( Type 2 or hosted VM).
The software layer providing the virtualization is called a virtual machine monitor or hypervisor. System virtual machines (sometimes called hardware virtual machines) allow the sharing of the underlying physical machine resources between different virtual machines, each running its own operating system. See also: Hardware virtualization and Comparison of platform virtual machines An essential characteristic of a virtual machine is that the software running inside is limited to the resources and abstractions provided by the virtual machine-it cannot break out of its virtual world. In contrast, a process virtual machine is designed to run a single program, which means that it supports a single process. A system virtual machine provides a complete system platform which supports the execution of a complete operating system (OS). Virtual machines are separated into two major categories, based on their use and degree of correspondence to any real machine. Current use includes virtual machines which have no direct correspondence to any real hardware.
3 List of hardware with virtual machine support.2.3 Operating system-level virtualization.2.1 Emulation of the underlying raw hardware (native execution).