Every business website gets updates regularly and you really don’t want your user to see the incomplete work and getting annoyed. Maintenance mode give you leverage to work on without taking your website offline. Once it is enabled all the users who are not registered or who are not logged in will get the Maintenance mode Screen.
Those who are logged in can see what going on in the back.
You can simply enable the maintenance mode of Security Press >> General Settings >> Maintenance Mode
Maintenance mode comes with visual editor so you can copy paste the HTML or you can simply put the text message of your choice.