Virtualization has similarities to emulation, but it is quite different as well. The main difference is that in virtualization, you need virtual machines. Both such things run their software in a very isolated environment, but virtualization focuses specifically on the entire isolation, whereas emulation puts the environment as the focus. This results in emulators being able to simulate a huge hardware range than any virtual machine will be able to. For example, you won't be able to run PlayStation systems on any virtual machine. But you will be able to run a PS emulator easily on a virtual Windows space or environment.  But this makes virtualization faster when compared with emulation. After all, the machine just uses the processing power to run an isolated-subsystem. As such the CPU isn't emulated and this increases the speed.