Idea Behind Feature
At times owners find they need to take a site offline to users but want to keep it hosted, maintenance mode allows you to stop all member activity while making changes to your website.
Enable... When enabled only admin will be able to actually log in.
Maintenance mode type This setting defines whether or not the maintenance page shown to visitors will populate from the database. Use the simplified content section if you know your database will be down during maintenance. If your database will not be down using the full template settings is safe.
All settings below the 'Settings Content' field will require the use of the database. These fields allow you to control the page design from admin with no coding skills. Click the blue titles for each settings definition.