The Notification Center provides iOS 9 users with a way to easily access all notifications―text messages, missed calls, calendar alerts, app alerts and more, compiling ‘em all in a single place. Also, in iOS 9, the iPad’s Notification Center has been split into two columns to take better advantage of its larger screen (especially that of the upcoming iPad Pro).
To open the Notification Center, put a finger atop the iPhone/iPad screen and pull down. Think of it like pulling down a window shade. To close the Notification Center, drag the handle at the bottom of its window up — or press the Home button.
When you open an app for the first time, it will ask if you’d like to receive notifications from it (assuming it supports the Notification Center). Go to Settings > Notifications to select if the app will notify you. You’re provided with several choices as to how the app will notify you.