I call these the Hidden/Shown icons, instead of Hide/Show, because the icons indicate the current state of an item, instead of indicating what will happen when you click on them. The Hidden icon indicates that an item is hidden from the students.
Clicking on it shows the item to the students. The Show icon indicates that an item is shown to the students. Clicking on it hides the item from the students.
If you want to remove an item from a course while keeping it for later use, or if you want to keep an item hidden from students while you're working on it, hide it instead of deleting it.
