iOS 9 made some changes in the way you switch from one app to another. For example, the App Switcher has new overlapping design. iPads sports three multitasking superpowers: Slide Over, Split Screen, and Picture in Picture (which should be really useful with the upcoming iPad Pro).
To open the App Switcher, double-click the Home button. If you have Multitasking Gestures enabled (in Settings > General) on the iPad, you can slide the tips of four fingers toward the top of the screen.
With the App Switcher open, “flick” left or right to find the app you wish to launch. Tap the one you wish to open. Icons for any available Contextual Apps appear in a bar at the bottom of the screen. Tap one to open it.
To force quit an app with the App Switcher open, flick left or right to find it. Flick the image toward the top of the screen and — voila! — it’s closed. However, keep in mind that there’s rarely any need to force quit an app. The only time you should force an app to close is if it becomes unresponsive or erratic