Unit Completion
A new feature that is available in the modules of a course is to complete a prerequisite module in order to move on to another one. This effectively means that in order to access a particular module you must first have completed a “designated” module by the course teacher. The module that is pre-required is marked with an hourglass on the right-hand side. On the contrary, the module following the pre-required one is marked in grey which informs you that the specific module is not available until you have completed a series of specified actions (e.g. attending a lecture, opening a document, participating in an exercise).
Looking at the contents of the section you will notice that the pre-requisite items that need to be completed are marked with the hourglass on the right.
So having successfully completed all the required actions of the module you can see that the labeling of the modules has changed and now the content of the next module is accessible.