Facebook 4 Mac, known as Facebook Pro for Windows, is an app that has all the same functions of your favorite social networking site. It doesn't require any installation and doesn't have any additional options.
The user experience is much like the traditional Facebook one: you can log in and read your news feed, send private messages, update your status or do anything else that you can using Facebook in a browser.
So what's the advantage of having Facebook 4 Mac? Because its an app, the icon is placed on your Mac Dock, making it easy to access Facebook even if your browser is closed.