What is System virtual machine?

In computing, a system virtual machine is a virtual machine that provides a complete system platform and supports the execution of a complete operating system. These usually emulate an existing architecture, and are built with the purpose of either providing a platform to run programs where the real hardware is not available for use , or of having multiple instances of virtual machines leading to more efficient use of computing resources, both in terms of energy consumption and cost effectiveness , or both. A VM was originally defined by Popek and Goldberg as "an efficient, isolated duplicate of a real machine".