Every time the topic of IBUs comes up, someone mentions that it is a measure of bitterness. Someone immediately corrects this person and clarifies that IBUs measure something that correlates to bitterness but not bitterness itself. It never becomes totally clear what IBUs really measure - and what that means to the imbiber. Will someone please clarify exactly what it is that IBUs measure, and explain what the consumer can ascertain from the listed amount of IBUs on a beers label? I once had it pretty well explained to me by a beer geek at a restaurant before I really became an advocate, but I can't recall exactly how it all went, and I'd like to see a clear explanation in these forums at long last so that others who are unclear on this can find an answer.