It seems to me there's a bait and switch of sorts that we play on kids. We tell them science can answer their questions about the world, or that they can use science to answer those questions, but it kinda can't. Keep digging and pretty soon you're lost in not-quite-accurate metaphors that may have nothing to do with reality and "we can tell you how it behaves, it's [pages of equations], isn't that good enough?"

It may be (probably is) that "what is this" or "why does it do that" are just meaningless questions, in the sense a child (or adult who hasn't re-calibrated their expectations of what science can tell them) means them. Which is interesting itself, I suppose, but at that point just go study philosophy and art, if that's why you were into science in the first place—and I think it's why everyone at least begins to be interested in science.

[EDIT] in particular it's frightening how fast kids' questions stymie an adult because the adult realizes that they're only a step or two away from "why is there something instead of nothing, and also what is something?" and... good lord, at that point seriously just go become religious or get really into philosophy or something, because you're outta luck, kid, sorry, we don't have any actual answers, just observations about what all this stuff does, but no we can't tell you what "stuff" or "does" are.