Hi @MaryRosso ...
I'm making a bit of an assumption here, but based on what you've written, it sounds like you might be a student? If this is the case, much of what you describe would be controlled by the instructor to make it visible (or not) to you and your classmates. It's entirely possible that the instructor purposely hid the "Discussions" course navigation menu from you and your classmates and chose to list the discussion topics on the "Modules" page instead. (The "Modules" page is where instructors can build out the structure of the course.) I would suggest that you reach out to your instructor directly to ask about these questions...as he/she may be able to provide better information than we can provide here in the Community...because we do not have access to your school's Canvas environment or any class(es) that you are taking.
I hope this helps a bit. Please let us know here in the Community if you have any other questions about this...thanks!