Allowing other people to add the App to their FB pages
From JReviews Documentation
If you created the Available Widgets menu item with the WidgetFactory Add-on, the same menu item will now list FB Apps as well:
Instead of the Get Code button for regular widgets, FB Apps have Add to FB Page button and visitors of your site that will click that button will be redirected to Facebook where they'll be able to choose on which of their FB pages the app will be added.