ELMS Terms allows you to create a glossary of terms for a course.  To add something to the glossary, highlight a word in created content and select add glossary term.  An important distinction between glossary terms and other highlighter items is that glossary items will automatically be scanned and associated to content globally once referenced in a course version.

For example: You find the word "Geodesic" to be an important concept.  You highlight the word, provide a definition for it and then anywhere in the course version that Geodesic is used, it will automatically be highlighted.  Clicking the word will slide open a tab on the right side with a list of the terms used in the content.  There is also a Glossary link for the course that aggregates all of these back to a table display.