The iPhone Do Not Disturb features allows you to silence calls, alerts and notifications anytime you don’t want to be disrupted by them. To access this feature, tap Settings and then Do Not Disturb. You will see a moon icon appear in your status bar to let you know that your iPhone is in “Do Not Disturb” mode. This icon will go away when the Do Not Disturb feature is turned back off.

To customize the iPhone Do Not Disturb feature, top on Settings, Notifications and then Do Not Disturb. You will see choices that will allow you to schedule times that the Do Not Disturb feature should be active on your iPhone; such as during work hours or other times that you don’t want any interruptions.

You can also allow some calls to come through even though the iPhone is on Do Not Disturb. For example if you have a family member that you want to get calls and notifications from even though no one else can contact you. You can also opt to have repeated calls placed into the “Do Not Disturb” mode so someone cannot continuously call you if you don’t pick up.

Source Apple Support