Beer in its basic form is made from just four ingredients: water, malted grain, hops and yeast. Water provides the base for all beer, and various minerals in the water contribute flavor and character to the beer. Malted grains provide sweetness, color and body as well as provide the sugars for the production of alcohol. Hops contribute bitterness to the beer and provide flavor and aroma. Yeast is used to ferment the malty sugars into alcohol, and also contributes flavor and character to the finished beer.
In addition to the four basic ingredients, a variety of flavor and other miscellaneous additives can be used in the brewing process to improve clarity, spice, add flavor and otherwise enhance the beer. Examples include spices for holiday beers, clarifiers such as polyclar and gelatin, minerals and acids to aid in mashing, and flavor extracts for fruit beers.