The multisite feature allows several sites to share one WordPress installation. You can activate this feature to allow end users to create their own sites and blogs on your original installation. Alternatively, you may want to use the feature to create your own multisite network. The sites can share the themes and plugins you’ve installed, but not modify them. The additional sites will also have separate media directories and database tables.
Administrators can activate this feature by adding a line of code to the site’s wp-config.php file. WordPress versions 3.0 and up support the multisite feature.
/* Multisite */ define( 'WP_ALLOW_MULTISITE', true );
Administrators can add this code to wp-config.php to activate the multisite feature.