Hypervisor
In plain terms
Software that creates and runs virtual machines on physical hardware.
Going deeper
A hypervisor partitions one physical server into multiple isolated virtual machines, each with its own OS, sharing the underlying hardware. It's the foundation of cloud computing.
Under the hood
Type 1 (bare-metal, e.g., ESXi) runs directly on hardware; Type 2 runs atop a host OS. Containers are lighter but share a kernel, unlike full VMs.
Examples
VMware ESXi, KVM, Hyper-V, Xen, VirtualBox (Type 2).
Think of it like...
Like a landlord dividing one building into separate apartments: each tenant lives independently, unaware they share the same foundation.