Some tropes can be pretty broad. Some can be so broad that even a specific form of them can be tropes by themselves. Let's say there was a trope for 'Juggling'. You realize that "Scarf Juggling" and "Knife Juggling" are pretty common as well, to the point where you can think of half a dozen examples for both. Those would be Sub-Tropes, while "Juggling" in general is their Super-Trope. In logic terms, "Juggling" is the genus, while the different kinds of juggling are the differentia; they share the same common theme in their definition, but they each have additional features that distinguish one from another.