@Switch Blayde
Doesn't SOL also use "Part" when it breaks up a single story into parts because it's too long?
SOL uses the term 'page' for that, which again is separate from a normal typewritten page, or even an html page, but it breaks the story around the 10,000 word mark, forcing you to click 'next' to continue reading the current chapter.
Here's a quick breakdown of the relevant publishing industry terms:
Chapter: An author-defined collection of related events regarding a single principal/event, whether that's a single day, a single encounter, or an initial encounter and all the sundry responses to it.
Section: Groups of chapters, grouped again by a single commonality linking the various chapters. (Also includes front and 'backmatter' pages like Copyright, Dedications and Appendices.
Paragraph: A single focus grouping of sentences either regarding a single though (if there are multiple thoughts by the same speaker), or separate speakers (i.e. a logical collection of observations, comments and descriptions).
Section Break: Something (usually a simple line) which divides chapters into separate groups/sections. These are determined by either a time change, a POV change or a location change, and not for any other reason (these are required to help readers make sense of what they're reading, allowing them to start each new part of the chapter fresh, without carrying over what just happened).
Subchapters: Breaking up or combining book chapters into different elements in a single chapter (whether in print on online usage). These are often used in addition to the normal chapter divides an author chooses, so may combine multiple chapters into 'reasonably-sized' online pages, or split chapters across multiple online pages.