hypervisor
also: virtual machine monitor (VMM), virtualization platform
A hypervisor is software that creates and manages virtual machines, allowing multiple operating systems to run simultaneously on a single physical computer by abstracting hardware resources.
A hypervisor is a virtualization layer that sits between physical hardware and virtual machines (VMs). It intercepts hardware calls from each guest operating system and allocates CPU, memory, disk, and network resources dynamically, allowing multiple independent OS instances to coexist on one machine.
There are two main types: Type 1 (bare-metal) hypervisors like KVM, Xen, and VMware ESXi run directly on hardware with no host OS, while Type 2 (hosted) hypervisors like VirtualBox and VMware Workstation run as applications within an existing OS.
Example: Using KVM on Linux, you can run three separate VMs—one with Ubuntu, one with Fedora, one with Windows—all sharing the same physical CPU and RAM. The hypervisor ensures isolation between them so a crash in one VM doesn't affect the others.
Hypervisors are essential for cloud computing, server consolidation, and testing software in isolated environments.