Activity completion
From MoodleDocs
Activity completion allows the teacher to set completion criteria in a specific activity's settings. A check (tick) appears against the activity when the student meets this criterion. The criterion might be viewing, receiving a certain score or a student marking it as complete.
Activity completion is enabled by default in new installations of Moodle 3.1 onwards.
Note: If you don't see an 'Activity completion' option when setting up course activities and sections, ensure it is enabled in your course settings and then check with the administrator that completion tracking is enabled in Site administration > Advanced features.