A join table (collection) contains common fields from two or more other tables (collections). It helps to create a many-to-many relationship.
This is what a join table looks like…
So the join table in this instance should be called students join classes and this stores each individual record as having a class and a student. This can then easily be filtered to show what students are on a course or what courses a student has.
Hope this helps. Its a little tricky to get your head around but once you do, you will be flying.