<p>An extension is a software 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.</p>

<p>The term extension is generic and the following specific extension types are available (listed alphabetically): <br>

Component (since ) – adds custom functions to your site that can be selected from menus<br>
Language (since ) – defines an additional language for your site<br>
Library (since ) – provides functions to be used by other extensions<br>
Module (since ) – shows nonessential data in a side box, possibly on multiple pages<br>
Package (since ) – bundles related extensions<br>
Plugin (since ) – modifies content in articles or provides functions to extend other extensions<br>
Template (since ) – define the look, feel, and navigation capabilities of your site<br>

<p>For an overview of the most important extension types and the functionality they provide, see <a  href="http://docs.joomla.org/Extension_types_(general_definitions)" 
        title="enter this page" 
        alt="enter this page" 
        target="_blank"
        rel="nofollow"> Extension types (general definitions)</a> </p>

<p><strong>Reference: <a  href="http://docs.joomla.org/Glossary" 
        title="read the reference" 
        alt="read the reference" 
        target="_blank"
        rel="nofollow">http://docs.joomla.org/Glossary</a>
</strong></p>