what does it mean when your car makes a grindind noise when tryin to start it?

It sound like the starter gear that is supposed to mesh with the flywheel gear is not engaging properly, I would have this checked by a shop before it ruins the teeth on the flywheel and will require removal of the transmission and flywheel to fix. Usually when they test a starter its on the work bench and they can't tell that the teeth of the gear isn't fitting the flywheel properly