Technically speaking this isn’t an emulator. Instead, it’s an open source version of the Windows API – the system that controls how a particular program interacts with Windows. To put it in very simple terms, it’s a bit like a Windows-to-Linux translator. Because of this set-up, you don’t need a copy of Windows to use Wine on a Linux PC.
Not all programs run well under Wine, but the manufacturer does provide a comprehensive database on its website to tell you whether a program should work at all, and how complicated it is to set up. At the moment, Microsoft Office 2002 is the latest edition of Microsoft Office rated Gold (meaning it runs efficiently and simply).
The biggest drawback is that there’s little to no support from software manufacturers for Windows programs run in this way.
As it’s free to download and use, Wine is definitely a good bet for people who want to try running one or two Windows programs in Linux.