What is a wine appellation?

Hello there! I'm Dr. Vinifera, but you can call me Vinny. Ask me your toughest wine questions, from the fine points of etiquette to the science of winemaking. And don't worry, I'm no wine snob—you can also ask me those "dumb questions" you're too embarrased to ask your wine geek friends! I hope you find my answers educational, empowering and even amusing. And don't forget to check out my most asked questions and my full archives for all my Q&A classics.
Dear Dr. Vinny,
What is an appellation? Is it the same as the name of the wine? Or is it the region, subregion or even the village where the wine is from?
—Ardavan G., Glion, Switzerland
Dear Ardavan,
An appellation is actually a little bit of all of those things, depending on how it's used and where it is.
Broadly, an appellation is a legally defined and protected area. The term is mostly used in relation to where wine grapes are grown, but there can be other uses as well—I’ve heard about appellation-specific chocolate or coffee, for example. Each country determines what defines an appellation, and in some cases, a wine is not allowed to list the appellation unless other standards are met—such as what grapes are grown, and how the wine is made.
In the United States, official appellations are called American Viticultural Areas, or AVAs. It’s pretty straightforward: 85 percent of the wine must come from the AVA listed on the label. It can get a little more precise, because there are AVAs and sub-AVAs. The Napa Valley AVA, for example, has more than a dozen smaller defined AVAs within itself, like Oakville or Rutherford. Russian River Valley and Chalk Hill are AVAs within the Sonoma County AVA, and so on.
Appellations can get a little more complicated in European countries, like France. There, the Appellation d’Origine Contrôlée, or AOC system, has rules about what grape varieties can be used, the ripeness, minimum alcohol levels and even how dense a vineyard can be planted or how much it can yield. There the appellation refers not just to where the grapes are grown, but what kind of wine it is.
Some appellations can get quite small: The Château-Grillet AOC in France's Rhône Valley is an 8.5-acre monopole, one of the rare appellations that is owned entirely by one winery and comprising just a single vineyard.
—Dr. Vinny