A guest virtual machine (guest VM) is the software component of a virtual machine (VM), an independent instance of an operating system (called a guest operating system) and its associated software and information.
The guest VM and the host VM are the two components that make up a virtual machine. The guest VM is the component that functions as if it were a physical machine and the host VM is the underlying hardware that provides computing resources -- such as processing power, memory, disk and network I/O (input/output), and so on -- to support it.
A virtual machine monitor (VMM) or hypervisor intermediates between the host and the guest VM. By isolating individual guest VMs from each other, the VMM enables a host to support multiple guests running different operating systems.
A guest VM is usually distributed across multiple hosts for load balancing.