Apple added several multitasking features to the iPad in iOS 9. Slide Over allows users to open a second app without leaving the one they're currently using. With Split View users can have two apps open and running side-by-side, and Picture in Picture allows users to watch videos while doing other things on their iPad, such as surfing the web.
Slide Over and Picture in Picture are supported by the iPad Air, iPad Air 2, iPad mini 2 and iPad mini 3. Split View is supported by the iPad Air 2.