"Extensions" is a general term in TYPO3 which covers many kinds of additions to TYPO3. The main types are:
- Plugins which play a role on the website itself, e.g. a discussion board, guestbook, shop, etc. Therefore plugins are content elements, that can be placed on a page like a text element or an image.
- Modules are backend applications which have their own entry in the main menu. They require a backend login and work inside the framework of the backend. We might also call something a module if it exploits any connectivity of an existing module, that is if it simply adds itself to the function menu of existing modules. A module is an extension in the backend.
- Distributions are fully packaged TYPO3 CMS web installations, complete with files, templates, extensions, etc.