Vermouth is a fortified wine flavored with aromatic herbs and spices using closely-guarded recipes. Some vermouth is sweetened; however, unsweetened, or dry, vermouth tends to be bitter.
There are three general styles of vermouth, in order from driest to sweetest: extra dry, bianco/white, and sweet/red. Sweet red vermouth is drunk as an apéritif, often straight up, as well as in mixed drinks like the Manhattan. Dry white vermouth, along with gin, is a key ingredient in the mixing of martinis. Red vermouths are sometimes referred to as Italian vermouths and white vermouths as French vermouths, although not all Italian vermouths are red and not all white vermouths are French.