I never knew much about bar stools until recently. It seems contradictory since we're a design company, but you'd be surprised at how much you can learn from your clients.
I've joked with friends that should they ever be shopping for bar stools, to bring me along. I can tell you all about them -- styles, features, finishes, materials, and more. I can tell you about kitchen bar stools, contemporary bar stools, leather bar stools, extra tall bar stools, you name it! I've gained so much knowledge, just from doing some copywriting & SEO work for one of our clients, Barstools2U.com.
It's interesting how you often learn so much beyond your job description when you do the kind of work we do. We have to really get to know our clients and their businesses, so that we can deliver the right kind of results in keeping with their goals and aspirations. Through that process, you learn new things and expand your own horizons.