Modular pages vs Page collections

Sorry, but

or are there any differences that I don't see yet? To me it is confusing that "pages" are called "modules" even though they are the same.

Well, you could say that modular pages are a special kind of normal pages. And yes, some terminology is confusing.

I just don't see the difference between a page looping through a collection of pages and a modular page that loops through "modules" in exactly the same way.

Why are these two different topics in the documentation when they are basically the same?