KVM QEMU

It is an open source machine emulator and virtualizer that can run OSes (operating systems) and programs made for one machine on a different machine by using Dynamic Translation. It works by a special recompiler which can transform a binary code written for a special machine (processor) into another.

QEMU achieves very good performance by executing the guest codes (codes from another machine) on the CPU. It supports virtualization while working in the Xen hypervisor or using the KVM kernel module in Linux.

 KVM (Kernel Virtual Machine):

This is a vitualization structure that turns the Linux Kernel into a hypervisor. It switches the processor into a new guest state. It mainly focuses on kernel module whereas QEMU focuses on hardware module. It also supports Paravirtualization.