Apple Internal Hard Drive Error
You really need to put this Mac in target disk mode and connect it to another Mac - or you can accomplish the same things buy installing a fresh copy of Mac OS on a USB external drive and booting that.

Once you're running normal Mac OS on another drive, you can run SMART Utility to see if your drive is having a hardware failure. If it is, time to replace it. If it's not, you should run a good drive repair utility like DiskWarrior. Unfortunately, while Apple's Disk Utility technically performs these functions, it's fairly useless at both.