Maintenance mode allows a site to be available on a public url but requires users to login in order to see the site. This way it cannot be accessed by unauthorised parties or indexed by search engines until it is taken out of Maintenance mode.
Enabling/disabling this function is restricted to Administrator and Super Administrator roles.
All user roles can use the site while in maintenance mode.
To enable maintenance mode for your website:
Your website displays the maintenance mode message for all site visitors, including anonymous site visitors and search engines.
To allow all site visitors access to your website, clear the Put site into maintenance mode check box on the Maintenance mode page, and then click Save configuration.