Xen is Virtualisation software. At present, full Xen support is not yet in the stock LinuxKernel but is getting closer. Firms such as RedHat already ship Xen-enabled Kernels.
The priviledged or host domain is referred as a dom0 or xen0 domain.
Unpriviledged or guest domains are referred to as a domU or xenU domain.
Part of CategoryXen