Cocktail bitters are combinations of bitter herbs, barks, and other botanicals in a neutral alcohol base designed to be added in minute quantities to give final layers of aromatic and flavor complexity to cocktails.
The most common type of cocktail bitters, aromatic bitters have their origins in the digestive and therapeutic tonics of the late 19th Century and were perfected during the golden age of cocktails in the early 20th Century. In recent years, the craft cocktail movement has inspired myriad faithful recreations, reinterpretations, and exotic experimentation using almost every conceivable edible or botanical ingredient.
Cocktail bitters are not to be confused with bitter liqueurs such as Italian amaros or fernets which have a higher sugar content and are designed to be consumed on their own or in cocktails. Due to their pungent bitterness, one would not drink cocktails bitters on their own, unless you are a bartender of course.