Hops are the flowers of the hop plant, primarily used in the brewing of beer. They add bitterness, flavor, and aroma, balancing the sweetness of the malt. Hops also have natural preservative qualities, helping to extend the shelf life of beer. There are many varieties of hops, each contributing unique characteristics to the final product. Some common types include Cascade, Saaz, and Centennial. The timing of hop addition during the brewing process can influence the beer's taste and aroma, making hops a crucial ingredient in crafting different styles of beer.