Cocktail bitters are concentrated flavoring agents made from various herbs, spices, and botanicals. They are typically used in small amounts to enhance the taste of cocktails and other beverages. Bitters can add complexity and depth, balancing sweetness and acidity in drinks. Originally developed for medicinal purposes, bitters have become a staple in mixology. Common types include Angostura bitters and Peychaud's bitters, each offering unique flavor profiles. Bartenders often use bitters to create classic cocktails like the Old Fashioned and the Manhattan, making them an essential ingredient in the art of cocktail crafting.