Extensions
Language Switcher
The language switcher module allows you to take advantage of the language tags that are available when content, modules and menu links are created.
This module displays a list of available Content Languages for switching between them.
When switching languages, it redirects to the Home page defined for the chosen language. Thereafter, the navigation will be the one defined for that language.
The language filter plugin must be enabled for this module to work properly.
To view an example of the language switch moduler module, go to the site administrator and enable the language filter plugin and the language switcher module labellled "language switcher" and visit the fruit shop or park sample sites. Then follow the instructions in this tutorial.
Latest Articles Module
This Module shows a list of the most recently published and current Articles. Some that are shown may have expired even though they are the most recent. Help
Login Module
This module displays a username and password login form. It also displays a link to retrieve a forgotten password. If user registration is enabled (in the Global Configuration settings), another link will be shown to enable self-registration for users. Help
Menu Module
This module displays a menu on the site (frontend). Menus can be displayed in a wide variety of ways by using the menu options and css menu styles. Help
Most Read Content
This Module shows a list of the currently published Articles which have the highest number of page views. Help
Subcategories
Components
Components are larger extensions that produce the major content for your site. Each component has one or more "views" that control how content is displayed.In the Joomla! administrator there are additional extensions suce as Menus, Redirection, and the extension managers.
Modules
Modules are small blocks of content that can be displayed in positions on a web page. The menus on this site are displayed in modules. The core of Joomla! includes 17 separate modules ranging from login to search to random images. Each module has a name that starts mod_ but when it displays it has a title. In the descriptions in this section, the titles are the same as the names.
Templates give your site its look and feel. They determine layout, colors, type faces, graphics and other aspects of design that make your site unique. Your installation of Joomla comes prepackaged with four templates. 
Plugins are small task oriented extensions that enhance the Joomla! framework. Some are associated with particular extensions and others, such as editors, are used across all of Joomla!. Most beginning users do not need to change any of the plugins that install with Joomla!.