I teach HTML, CSS, and JavaScript to high school students. I want to clearly distinguish for them when to use a <details><summary> pair versus a <dt><dd> pair. Obviously, there is a visual difference, but from a semantic point of view, I don't see a clear difference. Since I teach that HTML is supposed to be about semantics, I am confused as to when we should use which. Furthermore, both sets of tags clearly delineate the term we are defining, which makes the use case for the <dfn> tag obscure to me. If this is the wrong forum for these questions, please suggest a better one 
