When a virtual machine (VM) is created, it runs based on a non-virtual, actual machine – on a PC, for example. The VM is thus reliant on the physical hardware. For this reason, there is a layer between both levels which is responsible for its management: the hypervisor. The hypervisor is a software which assumes the management of the necessary resources. The program, otherwise known as the virtual machine monitor (VMM), assigns the main storage, fixed-disk storage, network components, and processor performance within the system. In this way, several and different virtual machines can run on a host system, while the hypervisor ensures that these don’t impede one another and that all of them have the necessary capacity.
Essentially, the guest system (therefore, the virtualization) does not notice any of the VMM’s organizational steps. The hypervisor abstracts the hardware in such a way that the VM originates from an established hardware environment. Because the requirements that depend on the running programs always change with virtual machines, the fact that the hypervisor can provide resources as needed is one of its essential benefits. The guest system doesn’t notice this either: The virtual machine is unable to recognize the existence of other machines that run on the same physical hardware.