Description of standard tables in joomla

Source : http://www.informit.com/articles/article.aspx?p=1728831&seqNum=9

Standard Joomla Tables

Table Name	Description	PHP Class
jos_assets	New table added for ACL in version 1.6. Includes a row for every component, Contains a row for every item that has ACL permissions. This includes a "Root Asset" for the global permissions, a row for every component, plus a row for every component category, and finally a row for every article. The "rules" column stores the group permissions in JSON format. This table is used whenever we check if a user is authorized to perform an action.	JTableAsset
jos_banners	Contains a row for every banner defined in the site.	none
jos_banner_clients	Contains a row for every banner client defined in the site.	none
jos_banner_tracks	Contains a row for every banner track defined in the site.	none
jos_categories	Contains a row for every category defined in the site. This includes article, banner, contact, newsfeed, and weblinks categories.	JTableCategory
jos_contact_details	Contains a row for every contact defined in the site.	none
jos_content	Contains a row for every article defined in the site.	JTableContent
jos_content_frontpage	Contains a row for every article assigned to the featured blog menu item.	none
jos_content_rating	Contains a row for every rated article in the site.	none
jos_core_log_searches	Contains a row for every search term logged by the site.	none
jos_extensions	Contains a row for every extension installed in the site. This includes component, library, module, plugin, template, language, and file extensions.	JTableExtension
jos_languages	Contains a row for every language installed in the site.	JTableLanguage
jos_menu	Contains a row for every front and back-end menu item defined for the site.	JTableMenu
jos_menu_types	Contains a row for every front-end menu defined for the site.	JTableMenuType
jos_messages	Contains a row for every private message sent in the site.	none
jos_messages_cfg	Contains a row for every back-end user who sets a configuration in the Components → Messaging → My Settings option.	none
jos_modules	Contains a row for every module defined in the system. A "client_id" column of "0" indicates it is a front end module, "1" indicates a back-end module.	JTableModule
jos_modules_menu	Mapping table to show which modules are assigned to which menu items. The "menuid" column indicates which menu items the module is assigned to, as follows: "0" means assigned to all menu items; positive integer means assigned to this one menu item; and negative integer means assigned to all menu items except for this menu item.	none
jos_newsfeeds	Contains a row for every newsfeed created in the site.	none
jos_redirect_links	Contains a row for every redirect created in the site.	none
jos_schemas	Contains a row for each extension that has made database changes during its installation, along with the latest installed version of the extension.	none
jos_session	Contains a row for every active session for the site.	JTableSession
jos_template_styles	Contains a row for every template style defined for the site.	none
jos_updates	Contains a row for every available package to be installed.	JTableUpdate
jos_update_categories	This table is used to categorize the updates. It is maintained automatically by Joomla.	none
jos_update_sites	List of update sites. This comes from the update XML file for each extension.	none
jos_update_sites_extensions	Mapping table that links jos_extensions with jos_updates. Contains a row for each combination of extension and update site where that extension can be updated.	none
jos_usergroups	Contains a row for every user group defined for the site.	JTableUsergroup
jos_users	Contains a row for every user defined for the site.	JTableUser
jos_user_profiles	Contains a row for every combination of user id and profile field. This table is used if you have the User – Profile plugin enabled.	none
jos_user_usergroup_map	Contains a row for every group that a user is a member of.	none
jos_viewlevels	Contains a row for every View Level defined in the site.	JTableViewlevel
jos_weblinks	Contains a row for every weblink defined in the site.	none

Figure 46: List of Joomla Database Tables