View Usage to see the amount of time your iOS device has been awake and in use since the last full charge. The device is awake if you’re on a call, using apps, listening to music, browsing the web, or sending and receiving email, or if an app refreshes in the background. View Standby to see the amount of time the device has been turned on since its last full charge, including the time the device has been asleep.
You can view the usage statistics for your iPhone, iPad, or iPod touch by tapping Settings > General > Usage.
Learn about background refresh and multitasking.
Learn about batteries on these devices: