The following clarifications can help you understand this document and virtualization technology.
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.