Although the word "app" takes us directly to Android or iOS applications (or Windows 8, but who cares) this app is designed to run on nothing else but a computer.
As generic as possible
You might be asking why would you need a Facebook app on a screen that can support the fully detailed Facebook page. Well, you're mostly right. You don't need it. Especially since Facebook Pro is nothing more than a dedicated browser with bare-bones functions that is limited to displaying nothing else but the Facebook domain (and a few news sites).
The window has back and forward buttons, Home (which is set to Facebook.com) and "Social Media News" which is a collection of RSS feeds (news) from different sites, such as Mashable.com or Gizmodo.com. There's not much else to say about it, unfortunately. However, although Facebook Pro is nothing more than an underdeveloped browser, it is a browser nonetheless. This means that you can manage an extra Facebook account without employing another browser or switching between accounts. This is the best use you can get of it.
Preset RSS feeds
You can log into a Facebook account
Pretty much useless
This application was made with the scope of capitalizing on the Facebook identity. It has pretty much no use unless you really want to manage multiple Facebook accounts at the same time, in which case you might be a freak. Peace!