Hop varieties are different types of hops used in brewing beer, each contributing unique flavors, aromas, and bitterness. Common varieties include Cascade, known for its floral and citrus notes, and Saaz, which offers a mild, earthy character. Brewers select specific hop varieties to achieve desired taste profiles in their beers. Hops are categorized into two main types: aroma hops and bittering hops. Aroma hops, like Citra, are added later in the brewing process to enhance fragrance, while bittering hops, such as Magnum, are added early to provide bitterness. The choice of hop variety significantly influences the final product.