A bitter is an alcoholic beverage that contains herbal essences, has a bitter or bittersweet flavour, and is typically flavoured with citrus. There are numerous brands of bitters, which were formerly marketed as patent medicines but are now considered to be aperitifs, digestifs and flavourings for cocktails. Bitter liqueurs are liqueurs and fortified wines that have a bittersweet flavour.
They're often mixed with soda and served as aperitifs. These liqueurs are sometimes called bitters, but they're not as intensely flavoured as the cocktail bitters that come in small bottles, which are normally measured out in drops. Popular brands include Campari, Fernet Branca, Dubonnet, Punt è Mes, Cynar, Suze, Jägermeister, and Amer Picon. More Information on Bitters