CNBackstageController is an derivative of NSWindowController and a special impelementation to show you the content you would like to see. The goal of CNBackstageController is to provide the developer a slightly different interface for presenting an application. It mimics the behavior you’ve just seen in Notification Center of Mountain Lion. Instead of showing a normal window and menu bar an application build with CNBackstageController offer you a behind the Finder-like desktop and will be shown with smooth animations. The common use is an application nested as a statusbar item that is not visible in the Dock.