Multitasking on Your iPad With Slide Over, Split View, and Gestures in iOS 11
Split View (aka Split Screen) is an exciting iPad-only iOS 11 feature that allows you to multitask with two (or even three!) apps open at once! Great if you are copying between apps, dragging a photo from the internet to an email, or referencing another program while you type. For this example, let's say I want Safari and my email open at the same time. First, I have Safari open. Then I swipe up from the bottom once, quickly, to bring up my dock which I've loaded with frequently-used applications (in this case, Mail). I then drag Mail up from the dock on top of Safari, and it floats above taking up about 1/3 of the screen. This is called Slide Over.
If I swipe down quickly from the top of the Mail tab, like a downwards flick on the line, I swap to Split View and the screen actually splits the screen between Safari and Mail (or Notes and Mail in my pic).
If I swipe and hold the dividing line, I can drag the line and change which app takes the majority of the screen, or set it to half and half. Bouncing down on the top of one of the apps makes it float again in Slide Over, and swiping right makes it disappear off the screen. Swiping left brings it back out. You can also slide your floating app from one side of the screen to the other. If you want three apps (you crazy person), put two apps in Split View and drag another up from the dock to float above them in Slide Over.
For even more options and instructions, see Apple's own article on multitasking https://support.apple.com/en-gb/HT207582, or check out this Cult of Mac article https://www.cultofmac.com/490710/slide-over-split-view-ios-11/
Multitasking not working? Check that it's enabled:
Go to Settings – General – Multitasking and Dock and make sure Allow Multiple Apps is ON.
Multitasking Gestures on iPad
In addition to being able to swap between apps with the Control Centre, you can also use gestures. When using an app, swipe left or right with four fingers (or all five) to switch to a previously-opened app. Alternatively, while using an app, start with your five fingers spread on the screen and pinch them together to go to the Home screen.
Apps also have app-specific finger combinations to create additional commands, check your app's instructions for more details.