I can't answer what Buddha Nature is. People use the word in a lot of different ways, it would really depend on the way the teacher uses the word. You'd have to ask that specific teacher. They might talk about an inner potential, they might talk about something that kind of is everywhere, but it's a term which I don't use. And if you haven't realized by now, I stay away from a lot of these sort of terms, because it's something I don't actually know. That's one of the reasons why I like Theravadin Buddhism so much. In this practice, you have the ability just to stay on the ground, without having to worry yourself too much about these kind of words, which, by definition, we can't actually know unless we are actually enlightened. So I prefer to stay away from those topics.