Opening and closing an app is easy, Tap the app to open it, and then press the Home button to close it. But when you exit, you’re not actually shutting down the app: You’re freezing it in place, or sending it to run in the background. This means that you can have multiple active apps running at any one time, and you can even switch between active apps without returning to the home screen.
Frozen Apps versus Background Apps Sometimes you need an app to keep doing something when it’s not in the foreground. For that reason, Apple uses several tools to allow apps to perform tasks in the background. One of these tools is the notification system; another allows music apps to keep playing while the user switches to another app; yet another allows tasks‚ such as photo uploads‚ to continue running in the background even if you switch out of the program performing the upload. If your third-party app doesn’t incorporate background features, it will freeze when you press the Home button‚ which is to say that it will remember whatever you were just doing when you re-open it, but it won’t process any data in the background.
You can quickly switch between apps by bringing up the multitasking bar. To do so, quickly double-press the Home button; the screen will slide up to reveal a bar of apps underneath, showing off the apps most recently run. To switch to a different app, tap on its icon.
In addition to holding a list of your most recently used apps, the multitasking bar has a couple of other neat shortcuts for your phone. Swipe right to bring up a secondary set of controls that let you lock your device’s orientation in portrait mode and control the audio currently playing on your phone (it defaults to the Music app, but you can also control audio from third-party apps). Swipe to the right again, and you get a slider for controlling volume.