From the static point of view, virtual machine is a kind of system software, known as the VMM. The core function of Virtual Machine Monitor is to intercept the call that the software give to hardware interface, and re-interpreted as a virtual hardware visit. From the dynamic point of view, the virtual machine is an independent computer system, including operating systems, applications and the state of the system that is currently running, and so on. According to the virtual machine’s host, virtual machine environment can be divided into parasitic virtual machine and classic virtual machine. Host environment is a running
environment of virtual machine.