There used to be a virtualization module on NS but that was dropped some time ago. There is still some information about NS hosting VM’s using KVM in the admin manual But this is very basic. (to put it mildly)
NethServer is a very nice distribution, but IMO there are other (better) ways to manage VM’s or even complete virtual environments like ESX(i), ProxMox, Xen, HyperV etc…
Personally I quite like ProxMox and have that running on my home server with several NethServer instances on top of that as VM’s.
IMO there are just better tools available. If it is just to do a quick install of some distro, I’d go with virtualbox (or VMWare Workstation if you like that one more) on a laptop or desktop. For production I’d use a more serious hypervisor like one of the above mentioned bare metal hypervisors.