Can hd digital discs be played on a mac

If you mean Blu-Ray video disks, not natively, since the Mac has neither a Blu-Ray drive nor software for playing Blu-Ray movies. There are aftermarket Blu-Ray drives you can buy, and some third-party software that purports to play Blu-Ray movies, but the reviews I've seen of the software have been very mixed, so read up on the offerings carefully before you spend your money. If you really want to do this, it may be more effective to run Windows, either in virtualization or via Boot Camp, and get one of the players for Windows. At least a couple of those are from less-dodgy companies and hence have a better chance of working for you.

If that's not what you meant, please post back and clarify.

Regards.