I know what you were referring to - my answer would be the same - it is an emulator.
It's not a full functioning operating system but a program to give the appearance of a specific OS. You can't boot it.
It will give you the feel of UNIX - but you won't be able to get it all since you are really running from Windows.
Windows isn't multitasking - UNIX is. Cygwin isn't multitasking because it's running on top of Windows.
That's why I mentioned "is it live or is it Memorex?" and riding - it gives the same feel, but it's not the same thing.