Do Not Disturb silences alarms and rings, stops haptic (vibration) alerts, and turns off visual notifications. Alarms and priority alerts will still work. You can schedule Do Not Disturb to turn on and off at certain times. You can also allow priority calls or notifications when Do Not Disturb is turned on. You might want to set up automatic Do Not Disturb settings during your normal sleeping hours but allow calls from your family to come through.