Some scientific terms are too deep to directly describe them in layman's terms in a reasonable number of words.

Also, what one reader calls a layman's explanation another calls gobbledygook.

That's one of the reasons for inventing hypertext. For example, https://en.m.wikipedia.org/wiki/Riemannian_manifold has a nice introduction paragraph, but it presupposes quite a bit of knowledge. If you want to know more, feel free to click some links to learn more.

And yes, things probably aren't presented in a way that is optimal for _your_ learning, but there is no way to do that for every reader.