I understand we can make SDL Tridion Reference Implementation (STRI) Modules which include Content Manager and Delivery-side functionality.
A module is just a package of your additional features or functionality. I'd say it is nice if it comes with a powershell script to install (or any other form of a installer), but if you add a readme.txt or install.txt with it, that could also be sufficient.
While a Module is a concept on the CM through creating a Folder under \Building Blocks\Modules and similair in the web application through a folder under \Areas, it really isn't anything else than what we make it. So if you have a UI extension that adds functionality then there isn't really anything stopping you from packinging it up as an installable entity and call it a Module.
