Modules are generally speaking extensions to one of the menus or pages of itslearning. Modules are commonly used to grant access to a tool outside the context of a course - for example a video library that users can access - or to grant access to a report.
There are a fixed number of places where module extensions can currently be added. These are listed below.
Menus
Main menu
Course menu
Pages
Administration
Supervisor
Status and Follow-up (course)
Assessment record/Gradebook (course)
Note that at this moment, module extensions do not support any of the LTI Advantage extensions, only LTI 1.3 core.