VPS mean ‘Virtual private server‘ which is isolated part of a dedicated server computer. VPS functionality could be few type like OpenVZ container, XEN or KVM.
If you want to use Windows operating system on these VPS you have to go with either XEN or KVM because of Windows does not support OpenVZ system. We believe KVM ( Keyboard Video Mouse) system is best for Windows operating system these are like dedicated resources for you OS. So When you use Windows OS in VPS that is called Windows VPS. You can find more about virtual private server here.