A virtual machine monitor (VMM), also known as a hypervisor, is a software program that creates and manages virtual machines (VMs) on a physical computer.

The VMM allows multiple operating systems to run simultaneously on a single physical machine, effectively partitioning the hardware resources and providing isolation between the different VMs. The primary function of a VMM is to abstract the physical hardware from the VMs, allowing them to operate independently of each other.

This abstraction layer enables VMs to run different operating systems and applications without interfering with each other.

The VMM also provides mechanisms for managing and allocating resources, such as CPU, memory, and storage, to ensure optimal performance for each VM. There are two main types of VMMs: Type 1, also known as bare-metal hypervisors, run directly on the physical hardware without the need for a host operating system.

Type 2, or hosted hypervisors, run on top of a host operating system and are typically used for desktop virtualization. VMMs play a crucial role in modern computing environments, enabling organizations to consolidate their hardware resources, improve resource utilization, and reduce costs.

They are commonly used in data centers, cloud computing environments, and virtual desktop infrastructure (VDI) deployments. Overall, a virtual machine monitor is a critical component of virtualization technology, allowing for the efficient and secure operation of multiple virtual machines on a single physical server.

Its ability to abstract and manage hardware resources makes it an essential tool for modern IT infrastructure.