Generally, "appellation" is a geographical-based term used to identify where the grapes for a wine were grown. Well-known examples include Napa Valley and Burgundy.
Specifically, an appellation refers to a legally defined geographical or political area that lends its name and associated distinction to products and crops grown or produced within the boundaries of that area. The rules that govern appellations can vary by state and country, as well as across national borders (as in the European Community). For example, in the United States, wine labeled with an appellation must be made with no less than 95% of its grapes grown wholly within that appellation.