The simplest definition of beer is this: it’s a beverage made of fermented cereal grains. Let’s go into a bit more detail, though. Beer consists of a minimum of four ingredients. The first is grain (usually malted barley, but other grains can be used), followed by hops (which cover a huge number of different types), water, and yeast. Lager is a type of beer that’s made in colder temperatures (between 35º and 50º F) with bottom-fermenting yeast, while ale is the other main category — it’s made in warmer temps between 60º and 70º F with top-fermenting yeast.