In our early stages of Canvas, we've found a bit of confusion among instructors (and sometimes students) differentiating between the Assignments and Modules indexes.
Both indexes look similar, you can create Assignments from Modules, Assignments can look as if they appear in both locations (even though the Assignment in a Module is just a reference to the real thing). I think the trouble comes from not knowing where to click sometimes, or wondering why an assignment is in different orders in either location.
I generally suggest that instructors think of the Assignment index as "All Assignments". I generally tell them that Modules is a way to present linear access to learning items including Assignments. That seems to work sometimes.
I'm considering the suggestion that hiding the Assignment index from students may be useful if they are utilizing Modules to list those.
If you have any ideas or past experiences in conveying the difference between the two, I'd love to hear it. I'm responsible for making some training content for instructors, so the more concise I can make the concept appear, the better.