>The QEMU package provides a processor and system emulator which enables users to launch guest virtual machines not only under the same hardware platform as the host machine, but also dramatically different hardware platforms. For example, QEMU can be used to run a PPC guest on a x86 host. QEMU dynamically translates the machine code of the guest architecture into the machine code of the host architecture.
QEMU does full hardware virtualization; in other words, it would allow you to run a MIPS guest OS inside an x86 host. This is useful, but slower than the alternatives…
KVM is a hypervisor that leverages QEMU for device emulation. I believe (going from memory) this device emulation is basically limited to VGA, disk controllers, etc.
So… unless you have a compelling reason (guest platform different from host), it would be best to use KVM and QEMU together