DND mode on Fitbit stands for "Do Not Disturb" mode, which is a feature that allows you to turn off all unnecessary notifications and alerts on your Fitbit device. When DND mode is enabled, your tracker wont receive any type of alerts, and the screen wont turn on. This feature is available on most Fitbit devices, including Fitbit Charge 5, Luxe, Inspire, and more. It is a useful feature when you want to avoid distractions during a meeting, workout, or sleep.