According to Microsoft, an operating system is:
i. all or part of an operating system instance, or all or part of a virtual (or otherwise emulated) operating system instance which enables separate machine identity (primary computer name or similar unique identifier) or separate administrative rights, and
ii. instances of applications, if any, configured to run on the operating system instance or parts identified above.
As if this isn’t confusing enough, there are also two types of environments – physical and virtual. A physical OS is configured to run directly on a physical hardware system, where the virtual OS is for virtual environments.
Here is where is gets a little MORE confusing – hardware to run virtualization software or provide virtualization services are part of a physical environment. A physical OS environment can also contain one or more virtual environments.
Thoroughly confused yet?