Hops are the flowers (also called seed cones or strobiles) of the hop plant Humulus lupulus. They are used primarily as a flavoring and stability agent in beer, to which they impart a bitter, tangy flavor, though they are also used for various purposes in other beverages and herbal medicine.
In the Middle Ages, beers tended to be of a very low alcohol content (small beer). In Europe, many villages had one or more small breweries with a barley field and a hop garden in close vicinity. Before this period, brewers used "gruit", composed of a wide variety of bitter herbs and flowers, including dandelion, burdock root, marigold, horehound, ground ivy, and heather.
Hops are used extensively in brewing for their antibacterial effect that favors the activity of brewer's yeast over less desirable microorganisms and for many purported benefits, including balancing the sweetness of the malt with bitterness, contributing a variety of desirable flavors and aromas.
The hop plant is a vigorous, climbing, herbaceous perennial, usually trained to grow up strings in a field called a hopfield, hop garden or hop yard when grown commercially. Many different varieties of hops are grown by farmers around the world, with different types being used for particular styles of beer.