Hops contain an essential oil with a very bitter flavor. This bitterness counters the sweetness from the malt to create a more balanced beer, and it also acts as a preservative. Beer makers can play with the ratio of sweet maltiness to bitterness in the final beer by adjusting the type of hops used in the brewing, when they're added to the wort, and how long they're boiled.
So when those beer buffs talk about hoppiness in beer, they're trying to identify the bitter flavors of that particular ingredient and how they work with the other flavors in the beer. To get a sense for hops flavor, try beers that are described as having a lot of hops or being high in hops. Work your way down to those lower in hops and see if you can pick out the flavor!
Which hoppy beers would you recommend trying?
Related: Beer Guide: What is Lambic Beer?
(Image: Emma Christensen for the Kitchn)