Joomla Extensions
From HwdMediaShare Documentation
The Joomla package consists of many different parts, which allow modular extensions and integrations to be made easily. An example of such are extensions called "Plugins". (Previously known as "Mambots".) Plugins are background extensions that extend Joomla with new functionality. The WikiBot, for example, allows the author of Joomla content to use "Wikitags" in Joomla articles which will auto-create dynamic hyperlinks to Wikipedia articles when displayed. There are over 3,500 extensions for Joomla available via the Extensions Directory.
In addition to Plugins, more comprehensive extensions are available. "Components" allow webmasters to perform such tasks as build a community by expanding user features, backup a website, translate content and create URLs that are more friendly to search engines. "Modules" perform such tasks as displaying a calendar or allowing custom code like Google AdSense etc., to be inserted within the base Joomla code.
Since it has been around longer, there are more extensions available for Joomla 1.0 than for Joomla 1.5, although native 1.5 extensions are becoming increasingly available. Some of the older 1.0 extensions can be used with version 1.5 if it is set to legacy mode.

