meaning of self-contained classes and carry-over between classes

[skystar30097]

What does it mean by boled faced phrases?

Each class and the material for it may have to be self-contained in terms of both the aim of the class and the material used, not allowing for carry-over between classes.

[Tdol]

Each class must be separate- no class should require materials or content from another.

PS Please post questions about teaching in this section. Thanks.