JED
From Joomla! Documentation
An extension is a package that extends your Joomla! installation in some way. A small selection of extensions is included with the default Joomla! installation but many more are available from the Joomla! Extensions Directory (JED)
- Directory: http://extensions.joomla.org
- Terms of Service: http://extensions.joomla.org/about-jed/terms-of-service
- Joomla! Extension Directory FAQs: Joomla! Extension Directory FAQs
- JED documentation: http://extensions.joomla.org/support/knowledgebase
- Forum: Extensions.Joomla.org Forum
- Vulnerable Extensions List: http://vel.joomla.org/