It's a silly question designed to throw people off balance. I dislike it. But if you look at it the other way, it's an easy opportunity for you to nicely package your value proposition (ideally in comparison to your competitors) in a few sentences e.g. "I'm a rare candidate that has experience in X but ALSO Y" or "I'm a new grad but I have X internships under my belt" or "I'm switching careers so I'm a junior engineer now, but I've functioned as a responsible adult in some other job before, which your other candidates haven't" etc etc.

It's also something that they'll end up using if they have to justify your hiring to other people, so there's value in making it good.