Definitons:
Course: 
A course is a course identified by its course code.
Activities: 
The activities involved in a single course. This can mean lectures, tutorials, and practicals.
The activities of a course are manditory to attend. You cannot, for instance, go to lectures but not attend tutorials
Section:
You can pick which section of a single activity you can attend.
For instance, in a Lecture activity, there can be Hoell's lecture section, Diane's lecture sections, etc.
You can pick to go 
