Do Not Disturb is a new feature that allows you to block all calls not included on an optional whitelist. You can customize your Do Not Disturb settings by going to Settings -> Notifications -> Do Not Disturb. Afterwards, you can turn it on by going to Settings and turning on the ‘Do Not Disturb’ switch. Just like Airplane Mode, this must be turned off manually, and cannot be scheduled to be turned off.
Have fun with your iPad!