Beer is an alcoholic beverage made from grains like barley, wheat and rice that is flavored with hops. The document discusses the history of beer brewing from ancient Babylon to modern times. It details the key ingredients of beer - barley, hops, yeast, water and sugar - and explains the brewing process which involves steeping, malting, fermentation and other steps. The document also covers different beer styles like lager, pilsner and ale which are categorized based on the type of yeast and flavors used.