There are 3 types of extensions. Which type is best suited for your tool will depend on intended use.

Use case

Extension type

Your tool is meant for teachers (or students) to select or create course content.

Optionally there is a result that should be send back to itslearning.

Application

Your tool allows users to insert content - such as videos or images - in a text editor, like for example add-ons in Microsoft Word or Google Docs.

Plugin

Your tool is a service that users should have access to in a specific context, such as within a course or as supervisor.

Module