How to Use iPhone Multitasking
While using an app on your iPhone, press the home button once to return to the home screen. Once this is done, any app that was designed (or updated) for iOS 4 will be closed on the screen but kept running in the background. You can go into another app, or come back to that app at a later time and find yourself right where you left off.
To Find iPhone Apps Running in the Background:
Double tap the home button. A strip of app icons will appear at the bottom of the screen (as shown below). Swipe to scroll through to find all the apps that are running in the background. In the example below the camera, calendar, calculator and a Twitter app are currently running in the background.
Using iPhone Multitasking to Switch Apps:
While inside of an app, double tap the home button. The multitasking menu will open at the bottom of the screen. Select the app that you wish to open. You will be taken to the new app and your previous app will be moved to the background. In the screenshot below the phone is switching from the CNN app to the iPhone calendar.
To Play Music While Using Other Apps:
iPhone multitasking enables you to listen to music while running other apps that have multitasking enabled. To play music in the background, open your music playing app (iPod, Pandora, etc). Select the music you wish to listen to. Double tap the home button and select the app that you wish to open next. Your music will continue to play even though the music app is not actively opened on the screen.