2. The four main ingredients of beer are grain, hops, yeast, and water
Just like baking bread, the ingredients that go into beer play huge parts in their own rights. Grains (usually malted barely, but sometimes a blend of rye, oats, or other grains) give beer the sugar needed for fermentation. Water (which, at 95% of the product, is often the unsung hero) has to be treated to make sure nothing affects flavor or fermentation, and allows for all of the chemical reactions to take place. Hops act as a preservative and provide the bitterness to counterbalance the sweetness of beer and give it beautiful aromas. Yeast is the actual worker behind it all, converting sugar into alcohol and actually creating beer.
The process is so tried and true it’s even been legislated: in Germany, purity laws called Reinheitsgebot have ensured the ingredients have stayed the same since the 1500s (although actually sticking to it these days is sort of considered to be optional).
3. Other ingredients are called adjuncts (as well as flavorings)
Wheat, oats, corn, rice, and sugar are regularly added to the mash to up the amount of fermentable sugar, build a beer’s body up or tone it down… or to cut corners. A lot of cheap beers are made using a huge amounts of corn and rice to save money on malted barely. Other ingredients are also very common, including spices like coriander and sage, coffee, chocolate, milk, fruit, or honey -- all of which have a more direct effect on the flavor of beer.