The AOC system
Wines have always been known by their place of origin. It's a useful shorthand for describing what they taste like.
Winemakers from the same area tend to work in the same sort of way and to have similar raw materials. The problem is guaranteeing that the wine in the bottle corresponds to the name on its label. The AOC system is an attempt to do that.
The authority responsibile for administering and enforcing the system is the Institut National des Appellations d'Origine.
For the last seventy years it has been carefully drawing a map of French wine. In theory, all of the country's best vineyard sites have been identified and categorized within a strictly hierarchical system.
The boundaries of the appellations are intended to reflect differences in soil, geology, and micro-climate. They are seen as the legal embodiment of terroir.
It is the land, not the wine (and certainly not the winemaker), that is classified. The wine changes from year to year, winemakers come and go, but one patch of land will always be Volnay.
Only wines tasted and approved by INAO, made in the style, and with the grape varieties, most suited to the area, are allowed to be labelled with their place of origin.
The name should be as much a badge of quality as a guide to style.
Wines that do not come up to standard, are atypical, or are grown outside the areas with full AOC status must be labelled in a variety of other ways.