This activity allows participants to create and maintain a list of definitions, like a dictionary.
The entries can be searched or browsed in many different formats.
The glossary also allows teachers to export entries from one glossary to another (the main one) within the same course.
Finally, it is possible to automatically create links to these entries from throughout the course.
How to add a glossary - https://docs.moodle.org/37/en/Using_Glossary