What role does bitters play in cocktails?

Bitters contribute a complex flavor profile in cocktails, which is essential for balancing and enhancing the overall taste of a drink. They are typically concentrated flavoring agents made from various herbs, spices, and botanicals, and they add depth and nuance to cocktails that may otherwise taste flat or one-dimensional.

When added in small amounts, bitters can help bridge different flavors and provide a counterpoint to sweetness or acidity, ultimately creating a more harmonious and intriguing drink. This complexity can elevate a cocktail, making it more enjoyable and sophisticated.

The other options do not accurately reflect the role of bitters. For instance, bitters do not add sweetness; they are generally quite bitter. They do not serve as a base spirit, as base spirits are the primary alcoholic components of cocktails. Additionally, bitters do not make cocktails fizzy; carbonation comes from mixers like soda or tonic water, not from bitters.