It's not just a figure of speech, it's a useful abstraction. The protons don't move, but the holes seem to do that. Not only that, if you pretend the holes have

It's not just a figure of speech, it's a useful abstraction. The protons don't move, but the holes seem to do that. Not only that, if you pretend the holes have a certain amount of mass you can predict how they move, and they move similarly to how a positibly-charged particle would move in the same circumstances.