You can easily swap between apps without having to close the one you’re using. Double-press the Home button quickly to bring up the multitasking view. This reveals your apps in the order they were last opened, each represented by a screenshot of the app itself.
You’ll see a bank of four recent apps, but you can swipe from right to left to see more. Tap on a screenshot to switch back to that app.
To close an open app, swipe up on the screenshot. Close multiple apps at a time by using two or three fingers – simple swipe up using the same motion to close them.