Multitasking, in the case of desktop computers, means running more than one program at a time. Multitasking on the iPhone works differently. The iPhone allows a few types of apps to run in the background, while other apps work in the foreground. Typically, iPhone apps are paused when you are not using them, and quickly come back to life when you select them.

Instead of offering conventional multitasking, the iPhone uses something Apple calls Fast App Switching. When you press the Home button to leave an app (or swipe up on the screen on an iPhone X or later) and return to the Home screen, the app you left freezes where you were and what you were doing. The next time you return to that app, you pick up where you left off instead of starting over.

Apps that are running in the background don’t use battery life, memory, or other system resources. For this reason, force-quitting apps that aren’t in use doesn’t save battery life. In fact, force-quitting suspended apps can actually negatively impact battery life. There’s one exception to the rule that suspended apps don’t use resources: apps that support Background App Refresh.

In iOS 7 and later, apps that can run in the background get even more advanced. That's because iOS learns how you use apps with Background App Refresh. If you normally check your social media first thing in the morning, iOS will schedule that behavior and update your social media apps a few minutes before you normally check them to make sure the latest information is waiting for you.