The Launch Cycle

https://developer.apple.com/library/prerelease/ios/documentation/iPhone/Conceptual/iPhoneOSProgrammingGuide/StrategiesforHandlingAppStateTransitions/StrategiesforHandlingAppStateTransitions.html

When your app is launched (either into the foreground or background), use your app delegate’s application:willFinishLaunchingWithOptions: and application:didFinishLaunchingWithOptions: methods.

At launch time, the system automatically loads your app’s main storyboard file and loads the initial view controller. For apps that support state restoration, the state restoration machinery restores your interface to its previous state between calls to the application:willFinishLaunchingWithOptions: and application:didFinishLaunchingWithOptions: methods.