Virtualization is a bit more - and less - than emulation.
Originally virtual machines covered emulating enough to run multiple operating systems on one computer. One of the requirements was that it was efficient, which pretty much precludes emulating the cpu. The 68000 didn't support virtualisation, but the 68010 did (i.e. MOVE from SR became privileged).
So for running windows on an intel mac you can use virtualisation software like VMware Fusion or Parallels Desktop. If you want to run windows on a power pc mac you need to run an emulator like Virtual PC 7
The term virtual machine has been used incorrectly over the years though, which muddies that water a little. The Java Virtual Machine for instance. It's not a real virtual machine in a lot of ways, but the name stuck. Technically all "operating systems" should be running under a hypervisor and not have any access to the hardware, this is largely impractical now though down to how operating systems and device drivers are developed. Windows Hyper-V Server is realistically the closest you can get.