key changesin the
stateof your app. Specifically, it responds to both temporary interruptions and to changes in the execution state of your app, such as when your app transitions from the foreground to the background.
responds to notificationsoriginating from outside the app, such as remote notifications (also known as push notifications), low-memory warnings, download completion notifications, and more.
restorationshould occur and assists in the preservation and restoration process as needed.
responds to eventsthat target the app itself and are not specific to your app’s views or view controllers. You can use it to store your app’s central data objects or any content that does not have an owning view controller.