In AirPort Utility, what is the menu item "Restore Default Settings"?
According to AirPort Utility 6.x: Reset your base station, it will reset your base station to Apple factory settings, meaning that you will lose your current setup and it'll be just as if you were setting it up for the first time out of the box.

Use this option if you're having issues with your base station and nothing else seems to be helping ... or when you're getting ready to sell it.