The term virtual machine refers to an instance of virtual hardware environment and the operating system that runs on that instance of virtual hardware. A virtual machine could be running any type of software, such as server, client, or desktop. It is often called a virtual computer, guest, domain U, domU, or unprivileged domain.

The term virtual machine server or VM Server refers to a physical computer and software that combines to host, create, and control virtual machines. It is sometimes referred to as a host, domain 0, or privileged domain.

The term virtual machine monitor (VMM) refers to the software layer that enables SUSE Linux to host virtual machines. It is sometimes referred to as a hypervisor. The VMM consists of software developed and maintained by the Xen open source community. The VMM is extended for full hardware emulation with QEMU software.

The term VM-aware refers to an operating system that is optimized for the virtual machine environment. It is often called a paravirtualized, Xen-enabled, modified or optimized guest.

Operating systems not optimized for the virtual machine environment are often called shrink-wrapped, out-of-the-box, unmodified, or fully-virtualized guest.