When I first started studying music, there were a lot of things that confused me. It felt like there were whole languages of practice that musicians all knew, and I had no idea how to speak any of them. With a lot of work and some very patient teachers, I eventually got fluent, but one problem that stuck with me is, in hindsight, a fairly simple question: What's the difference between 3/4 and 6/8? It feels intuitive now, but in order to understand it you have to really understand meter, and that's a lot harder than it sounds.