Grabbers, like the one in the photo above, appear while trying to invoke Notification Center or Control Center in a full screen app. The grabbers essentially force you to perform two invoking gestures in order to launch Control Center or Notification Center. The grabber feature is there to prevent accidentally launching the aforementioned overlays while using a full screen application or game.
Some people, apparently, find the grabber feature annoying, and they want to launch Notification Center or Control Center like they normally do, even while using a full screen app. If you're one of those people, then NoGrabber is something you should consider using. It forces the overlays to behave like normal, eliminating the grabber while in full screen applications. Take a gander at our video walkthrough to see how it works in action.