The layer between software and hardware
A hypervisor is software that divides a computer’s physical resources—its processors, memory, storage, and network connections—among virtual machines. Each virtual machine behaves like a separate computer, with its own operating system and applications. The hypervisor sits between those systems and the hardware, deciding which machine gets access to which resources.
When one virtual machine needs to run a program, the hypervisor schedules its work on the physical processor. It also gives the machine a defined slice of memory and presents virtual disks and network interfaces. Those devices look real to the operating system inside the virtual machine, even though they are backed by shared hardware.
Sharing without mixing
The separation is enforced through hardware protections and the hypervisor’s controls. A program inside one virtual machine normally cannot read another machine’s memory or alter its files. That isolation lets organizations run different operating systems, or separate workloads, on the same server without treating them as one shared software environment.
The machines are not independent of the limits of the hardware. If several workloads demand more processor time or memory than the computer can provide, they compete and performance can suffer. The hypervisor can distribute resources, but it cannot create more physical capacity.
Why the arrangement matters
Without virtualization, a server often had to be dedicated to a single operating system or workload, even when much of its capacity sat unused. A hypervisor makes it practical to consolidate those jobs: one physical server can host many virtual machines, and administrators can manage each as a distinct system. The key tradeoff is simple: more flexible use of hardware in exchange for sharing its finite resources.
