Courses are divided into sections. What constitutes a section depends on the course's format. There are two main important formats:
For your first few courses, especially courses based on existing non-e-learning material, these are likely to be the only two you use. However, there are others:
SCORM and LAMS—These are for working with e-learning 'standard' formats. If you know what they are, they are useful. If you don't, then you won't need to.
Social format—The whole course is built around a single forum. This is useful for using Moodle to manage things that are not strictly courses. You could use it to set up a departmental notice-board, or a discussion forum for an after school club.
Weekly format (CSS/No tables)—This is a variation on the weekly format. You can usually ignore it, but if the usual weekly format doesn...