Understanding Open edX courseware organization
When building a course in Open edX, it's helpful to understand how things are organized.
Courseware in Open edX is comprised of Sections, which are made up by Subsections, which are made up by Units.
When working in Open edX Studio, this is what sections look like when they are collapsed. Sections are the highest level of organization and generally are used to divide content up into things like Chapters or Weeks.
You can expand Sections to see more clearly how your course is organized.
It should be noted that grading is configured at the subsection level. So if you are creating a subsection that will have a quiz unit within it, be sure to set that subsection to be graded as a Quiz. More on grading here.
By clicking on a unit, we see that this is where all of the authoring happens. Within each unit, you can add components to create content.
Here's what things looks like from the LMS side.
As you can see, it's really easy to navigate around the course right from within any unit.
That's the gist of things. You can organize your course however you want - by topic, by chronology, by chapter, etc. It's completely up to you.