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A hypervisor manages system virtual machines, giving each guest a virtual machine interface while controlling its use of physical resources. It mediates facilities such as processor execution, computer memory and devices so that several guest operating systems can share a host. Hardware-assisted execution can run many guest instructions directly while retaining control over privileged operations.^[ref]

For example, a guest's apparent physical address need not identify the same physical storage as the identical address in another guest. Separate mappings preserve their distinct computer memory contents. The hypervisor must also schedule execution and enforce device-access rules. Providing a separate guest operating-system kernel distinguishes this interface from ordinary software containers sharing the host operating-system kernel.

A virtual machine presents a specified machine interface implemented using another system. A system virtual machine supplies virtual processors, memory and devices to a guest operating system. A hypervisor mediates access to the underlying resources; execution can combine hardware assistance and software emulation.^[ref]

For example, a guest can maintain its own kernel and filesystem view while a host schedules several guests on one physical machine. A Java virtual machine instead exposes a bytecode execution model to programs, illustrating a different level of abstraction. A container usually shares the host kernel rather than supplying a separate full guest kernel. The interface being virtualized determines which compatibility and isolation properties a particular virtual machine provides.