France is the world's second largest wine producer behind Italy. The wines produced range from expensive high-end wines sold internationally to more modest wines usually only seen within France. Two concepts central to higher end French wines are the notion of "terroir", which links the style of the wines to the specific locations where the grapes are grown and the wine is made, and the Appellation d'Origine Contrôlée (AOC) system. Appellation rules closely define which grape varieties and winemaking practices are approved for classification in each of France's several hundred geographically defined appellations. France is the source of many grape varieties (Cabernet Sauvignon, Chardonnay, Pinot Noir, Sauvignon Blanc, Syrah) that are now planted throughout the world, as well as wine-making practices and styles of wine that have been adopted in other producing countries.