Virtual Machine

A virtual machine (VM) is a software-based computer that runs its own operating system and applications on top of a physical machine. Software called a hypervisor, such as VMware ESXi, Hyper-V, KVM or VirtualBox, shares the physical hardware among several VMs.

Each VM is isolated, so different operating systems can run side by side on one server, which improves hardware use. Cloud servers such as AWS EC2 are VMs. Compared with containers, VMs are heavier, because each includes a full operating system, but they offer stronger isolation.