If I were to ask you: "Parlez vous francais?" you would have a number of answers available to you according to your situation, without much thought being needed, such as "oui", or "non", or "un peu", or perhaps you would answer in English that you don't speak French. You would not ask "What do you mean?" because the original question is self-explanatory. But if I were to ask you "Do you speak music?" You might well think that this was a very unusual question, and wonder how to interpret it. The reason that I am asking this seemingly opaque question is that I believe everybody has an innate understanding of music, and therefore it follows that my question is really a rhetorical one, to which everybody can answer "Yes".