What does the term "bitters" refer to in mixology?

In mixology, the term "bitters" refers to a concentrated flavoring agent that is used to enhance the taste and complexity of cocktails. Bitters are made by infusing various herbs, spices, and other botanicals in alcohol, resulting in a distinctively aromatic and flavorful liquid. Just a few dashes of bitters can significantly alter the flavor profile of a drink, adding depth and balance by introducing bitter, botanical, or spicy notes. This is essential for many classic cocktails, where bitters serve to round out the flavors of the other ingredients.

The other options don’t correctly describe what bitters are; for example, sweeteners are used to add sugar or syrupy sweetness to cocktails, garnishes visually enhance drinks and add some flavor, while carbonated mixers like soda or tonic water provide bubbly texture but do not contribute the complex flavors characteristic of bitters. Therefore, the role of bitters as a concentrated flavoring agent is integral to creating well-balanced cocktails.