Cabernet Sauvignon is a thick-skinned, black grape producing the most classic, age worthy (and needing of aging) red wines. Typically has flavors of fresh herbs (often quite pronounced), cedar, cassis, mint, black currant, and violets. Usually full-bodied wines, cabernet is often astringent when young due to mouth puckering tannins (a product of the grape skins that helps wine age).
Cabernet Sauvignon is found in many locales, most notably in California and red Bordeaux -- particularly in the Medoc, including Pauillac, St. Julien and the famous classified growth Bordeaux -- and is labeled cabernet sauvignon in South America, Australia, Italy and Washington. It's also in Italy's "Super-Tuscan" wines but usually not labeled cabernet.