I talked with a guy who said the crankset on the bike he is selling is "stripped."

I asked him what he means, and he said it turns, but doesn't turn the wheels. Assuming he has a chain, and it's connected ( ), I'm thinking that something is wrong with the freewheel, and at worst, I may need to replace it. What say ye experts- any ideas on what might be going on with this "stripped" bike?