It's no emulation - you need a windows license (same like bootcamp) - there are solutions like wine bottler, but if you need windows for more windows-only programs I would use another solution. To name three - VirtualBox - VMWare Fusion - Parallels I'm prefering the VMWare Fusion - it's 60€ with a 30 day demo - VirtualBox is for free and I don't know the price of Parallels. If you're not using other windows programs you may start with VirtualBox.
If you want to run windows games on a mac a virtual machine might not work as expected - then you've to use bootcamp and rebooting to play the game.