multisite

Multisite is a so-called "mode" built into the engine that allows creating a network of multiple websites, running on a single installation.

WordPress Multisite Network Features:

• You may have a network of multiple WordPress blogs and websites based on one WordPress installation.

• You can open WordPress Multisite Network for other users. They will be able to create their own blogs.

• You can set a network of subdomains like http://site.example.com or http://www.example.com/site/.

• In standard WordPress installation, the administrator role has the highest permissions on the site. Multisite has an administrator role for each site, but it also has a super administrator role. The super administrator has access to every site on the network, and is able to manage everything on every site. As a super administrator you can make changes to themes for all websites. Website administrators can not make changes to their themes.

• Each site may have its own content, users, plugins and themes. All those features are provided by single WordPress installation.

You may find more information regarding WordPress multisite feature in WordPress documentation.