Joomla Multi Sites / Multiple joomla configuration

Joomla Multi Sites allows multiple domain names or sites to have their own joomla configuration file using the same joomla installation. With this new feature you can share the same joomla installation directory and create different web sites. As each site has its own joomla configuration, you can easily decide to share the same database and use a special database prefix (other than "jos_"). The setup of each configuration site consists in using the standard joomla installation mechanism. In the administration of a 'Slave' site, you can re-install/uninstall extension previously installed on the 'Master' site. The 'Master' site is the one where you have installed the Joomla MultiSites component and where you manage the 'Slave' sites. Additional control are performed during the installation/uninstallation of an extension in a 'slave' site. Before executing the standard joomla installation, it is verified that the extension you request to install has exactly the same name and same version number to avoid inconsistency between all sites. This additional control is performed to ensure that you will overwrite the current installation with identical files that you originaly installed. On 'slave' site, the uninstall of an extension consists in a joomla standard cleanup of the database. The files present on disk for this extension are not deleted to avoid disturb the other sites. Templates and Languages are automatically shared between all sites. The re-installation of thoses extension is therefore disabled from the 'Slave' sites. Joomla Multi Site is a Joomla native 1.5 component.

Original Source: Joomla! Extensions Directory