In virtualization technology, the term virtual machine refers to an emulator that mimics dedicated hardware. A virtual machine enables a single physical host computer to run multiple guest operating systems simultaneously.
In business contexts, virtual machines are often managed by a specialized piece of software called a bare-metal hypervisor, which is used to manage virtual machines and assign dedicated hardware to them. Bare-metal hypervisors are used in cloud computing platform providers, where they ensure the scalability of virtual cloud service infrastructure. For example, a Web service hosted on virtual machines provided by an Infrastructure as a Service provider such as Amazon Elastic Cloud can easily spin up additional virtual machines to cope with increased website usage during busy periods. This ability to quickly scale the amount of dedicated hardware in use has many business and cost advantages when compared to using dedicated hardware with single host operating systems.
Virtual machines are also used by home desktop and mobile users to utilize software that is incompatible with their host operating systems. Parallels Desktop and VMWare Fusion are popular virtualization software options for Mac users who wish to use Windows software. Oracle VM Virtualbox is a cross-platform product that allows a host system to run guest operating systems such as Windows, Mac and Linux.