Hi @lukekm ...

Unlike @Gabriel33, I do have this "Export Course Content" button available at the top of my "Modules" page (not the "Home" page).  I haven't really used that button before, so I tried it out.  The export produces a *.zip file, and most of what I found is any and all files from within a course's "Files" page.  Once you unzip the *.zip file, you'll click within a folder or two, where you'll eventually see an "index" (HTML) file.  If you open up that file (it should launch in your browser), you'll see a page which looks similar to your "Modules" screen layout that you're normally familiar with within Canvas.  The links on this "index" page do work, so if you had a page in your course, you could click on the link to that page in your "Index" page, and it should show the content on the related page.  The "index" page looks like an "offline" view of your course.

However, as you've noted, there is a different way (via your course "Settings" screen) to export your course.  That method produces a *.imscc file for you to download.  Once downloaded, you can change the file extension from *.imscc to *.zip.  Once you unzip the *.zip file, you'll find that the folder structure is quite different.  There will be lots of folder and files with long strings of alpha-numeric characters.  (Those are each of your assignments, by the way.)  The "wiki_content" folder will have information about your course "Pages" content pages, for example.

I, too, am not sure where any documentation would be related to the button on the "Modules" page.  I couldn't find anything in my own searching.  😕

I hope this will be of some help to you.