Define when an activity or material should be considered complete. This allows students to see which activities and materials still need to be completed. As a teacher, you can also make the completion of certain activities a prerequisite for displaying further materials or activities.
Course settings, Completion tracking section:
You can then define individually in each activity:
See also on Moodle.org: Activity completion settings.
The conditions for completing an activity are displayed to students in the activity.
Optionally, the completion conditions can also be displayed on the course main page (“Show activity completion conditions = Yes”).