Beer is made with malted grain (usually barley), water, yeast, and a flavoring. That flavoring is usually hops (the dried cone-shaped flowers of a vining plant), whose bitterness counters the sweetness of the malt. Different flavors and beer styles are achieved by using malts that have been roasted to various degrees, by choosing different types of yeasts and hops, and by controlling when the hops are added. The taste of beer also can be changed by using other grains, such as wheat, in addition to barley. Many American beers include corn and/or rice to lighten the taste and lower the price.

Beer is divided into two basic types: lagers and ales. Lagers are made with special strains of yeast that sink to the bottom of the brewing tank. Lagers are fermented and stored at cold temperatures. They tend to be light in color, with a subtle crisp, clean taste.

Ales often are fermented with yeasts that sit atop the tank and prefer warmer temperatures. These yeasts ferment more quickly and produce beer with fruitier flavors and more yeasty and malty aromas. Ales are made with more hops and have an earthier, stronger, more complex taste than lagers. There are many styles of both lagers and ales.