Virtualisation in the modern world is useful for using spare server resources and allowing a server to perform multiple roles. This allows multiple virtual servers on one physical machine. Saving on infrastructure costs. A server machine can be a very expensive investment and if it can be used for multiple virtual roles instead of just one; this makes more efficient use of the hardware. There is the possibility of creating a virtual server for a certain role and then deleting the server afterwards. This is a good way to test a new server role or software without dedicating a new machine for this task. Something like this would be very good for developing a new piece of server software and testing it in a virtual environment. Virtualising an operating system also allows testing an open-source distribution on a server and have the ability to create snapshots of the operating system state. This allows a very quick rollback if something goes wrong. HyperV Server is a great way to roll out virtualized server/desktop instances with a high-specced server running virtual desktop operating system instances. This is very convenient. The server can be in a secure location free from prying eyes.
But still serving out desktop OS instances to desktop machines on the same network. This is amazing. You can even run Ubuntu on a HyperV server. Once I was setting one up and I installed MS-DOS on it. Not very useful but it could run Doom. For Linux, there is oVirt, which allows a server to run virtual machines and then serve them out over a network. A very powerful tool for providing desktop environments from a server to clients on the network. If you used snapshotting to backup virtual machine images, then you could easily roll back an instance if something goes wrong with it. Saving time and effort recreating a users environment, and allowing them to get back to work sooner. VMware vSphere Hypervisor is yet another alternative, this is installed as a bare metal Hypervisor and can serve out operating system instances from a powerful server easily. Virtualizing servers makes for more efficient use of computing resources. They can easily be turned on and then off again when not required. The KVM virtual machine manager on Linux, virt-manager is able to be remotely managed over SSH and allows remote connection by a client to the server over a network.
Remote connection to a KVM virtual machine may be accomplished with VNC. But VMware vSphere Hypervisor is still preferred, this allows proper remote connection using the preboot execution environment (PXE) to boot an ESXi host from a network device if your host uses legacy BIOS or UEFI. The same way you use PXE boot with HyperV server to load a remote virtual machine over the Local Area Network. This is simple to configure.