What beer is

Beer is fermented grain - nearly always malted barley - flavoured with hops. Four ingredients do nearly all of it, and each is a dial you can turn independently, which is why a handful of inputs produce hundreds of styles.

• Water. Mineral content changes how bitterness reads, which is why Burton pale ales are hoppy and Pilsen lagers are soft. The towns had different water long before anyone knew why it mattered.
• Malt. Barley, germinated then kilned, which means dried with heat to stop it growing. How hard it is kilned is the dial: pale malt gives bready sweetness, medium gives caramel and toffee, and roasted-to-black gives coffee and chocolate. Malt is where beer colour comes from - not from strength, and not from the yeast.
• Hops. The seasoning. Bitterness to balance malt sweetness, plus aroma. Boiled early they give bitterness and lose aroma; added late or after fermentation they give aroma and almost no bitterness. That timing split is most of what separates a bitter old-school IPA from a modern juicy one.
• Yeast. Eats the sugar, makes alcohol, and throws off flavour compounds while doing it. The biggest single difference between beers, and the subject of the next chapter.

1. 1Mash. Crushed malt steeped in hot water so its starch converts to sugar. The sweet liquid drawn off is wort.
2. 2Boil. Wort boiled with hops. Sterilises it, and sets the bitterness by how long the hops are in.
3. 3Ferment. Cool, pitch yeast, wait. Days for a warm ale, weeks for a cold lager.
4. 4Condition. Rest it so flavours settle and carbonation comes up, then filter or leave it hazy.

Compare that to Part I and the shape is familiar. Beer is the fermented wash a grain whisky would be distilled from, stopped one step early and hopped. That's not a coincidence, and it's a useful way to connect the two.