Bitters are highly concentrated liquid extracts made from herbs, spices, fruits, and other botanicals, known for their strong, bitter flavor. In the context of alcohol and cocktails, bitters are used to add depth, complexity, and balance to drinks by counteracting sweetness and enhancing other flavors. They are an essential ingredient in many classic cocktails, such as the Old Fashioned, Manhattan, and Negroni. Common types of bitters include Angostura, orange, and Peychaud's. Just a few drops of bitters can transform a cocktail, making them a crucial component in the bartender's toolkit.