These are number of examples of how access to resources can be controlled.

Pre-requisite Study

This is probably the most common scenario in which there is content that the student must "complete" before they can move on to further content. 

A common case at present is ensuring that students have accessed safety guidance for labs before being given access to any of the lab activities. This at least puts in place a mechanism to ensure the students have had the safety briefing presented to them.

Tiering Content

There may be scenarios where different levels of content should be presented to students at different levels.

How to assign students to different levels can be done in different ways, but a common approach would be to allocate students to different groups, e.g. Novice, Intermediate, Expert.

The content that is relevant to each level then uses a group restrict access condition to only display the appropriate content to members of each group.