Bordeaux has a number of micro-climates resulting from the interaction of climate, soil and practices improved throughout history. A vineyard's position, topography and vines have resulted in a definition of specific terroirs to express the vineyard's potential and the varieties grown. The notion of terroir, very local, defines the “cru”, synonymous with properties in Bordeaux. The combination of a delicate and not very productive vine variety and almost barren soil, which makes the vine “suffer”, produces high-quality wines with specific properties.

Five classes of Bordeaux wine were established at different points in time. The notion of classification applies to wines and properties in the same region and of the same appellation. Thus, there is no classification system for the 57 appellations d'origine because these wines are all produced in various regions and conditions.

Over time, these legally defined classifications have become benchmarks, though fundamentally subjective ones. Each new vintage feeds debates amongst professionals and consumers alike about its properties. Even though these classifications were established at specific moments in the history of the Bordeaux vineyards, their influence can still be felt, especially via the ratings of the estates, which fluctuate from year to year. The revision of these classifications inspires passionate debate.