For many, emulation and virtualization go hand in hand, but there are actually some really key differences. When a device is being emulated, a software-based construct has replaced a hardware component. Its possible to run a complete virtual machine on an emulated server. However, virtualization makes it possible for that virtual machine to run directly on the underlying hardware, without needing to impose an emulation tax (the processing cycles needed to emulate the hardware).
With virtualization, the virtual machine uses hardware directly, although there is an overarching scheduler. As such, no emulation is taking place, but this limits what can be run inside virtual machines to operating systems that could otherwise run atop the underlying hardware. That said, this method provides the best overall performance of the two solutions.
With emulation, since an entire machine can be created as a virtual construct, there are a wider variety of opportunities, but with the aforementioned emulation penalty. But, emulation makes it possible to, for example, run programs designed for a completely different architecture on an x86 PC. This approach is common, for example, when it comes to running old games designed for obsolete platforms on todays modern systems. Because everything is emulated in software, there is a performance hit in this method, although todays massively powered processors often cover for this.
Both methods are used for various purposes and are sometimes confused, so be aware of the differences.