what is hops in a beer

I watched a first-time commercial brewer lose an entire 15-barrel batch of West Coast IPA because he treated the green pellets like a spice rack instead of a chemical reaction. He spent months planning the recipe, bought the most expensive Citra and Mosaic on the market, and then dumped them into the boil at the wrong temperature and the wrong time. By day 14, the beer didn't taste like tropical fruit; it tasted like boiled cabbage and aspirin. He'd spent nearly $5,000 on ingredients