A Joomla extension is an installable software part that adds or changes CMS functionality. Extensions can be supplied with the core or by third-party developers.
Main types
Components manage functional areas, modules display blocks, plugins handle events and templates provide presentation. Joomla also supports language packs, libraries and packages containing several extensions. One product can consist of multiple extension types.
Installation and maintenance
Use the standard Joomla extension installer. Check the source, CMS and PHP compatibility, dependencies, updates and licence before installation. Extensions may create their own tables, files and settings, so review data retention before removal.
Extension count alone does not determine Joomla site quality. Each part’s necessity, maintenance and tested interaction with the rest of the system matter more.