It's the buying/selling age. There is technically no legal drinking age in France, but rules about minors (parent responsability under rule of "common sense", parent must be present if under 16, illegal to have the minor drunk no matter what).

Eg your parents giving you a small glass of champagne at new year when you're 12 is legal.

It's not that dissimilar in the UK, or at least that was the case.

IIRC the drinking age on private property in the UK is 5 years. So there is a limit :P