Ever seen the temporary warning sign that reads "Working in Progress"? These notice boards are meant to inform people of the location's present condition. What if you wish to use a notion like this in your Magento 2 store?
Yes, it is achievable thanks to the maintenance mode feature.
A quick fix for temporary problem notifications that invite all customers to return later in maintenance mode.
When installing a new theme, configuring an extension to alter website behavior, upgrading to the most recent version of Magento 2, implementing certain customizations, or correcting a security vulnerability, you might want to enable maintenance mode.
Simply turning on maintenance mode temporarily displays users' damaged websites. Visitors receive maintenance-enabled notice messages in their web browsers rather than the store when Magento is in maintenance mode. Authorized IP addresses can, however, continue to visit the business regularly.
For more information, Visit: https://meetanshi.com/blog/enable-or-disable-maintenance-mode-in-magento-2/