Manage life-cycle events for your app and respond to the creation of multiple instances of your app's UI.
In iOS 13 and later, the user can create and manage multiple instances of your app's user interface simultaneously, and switch between them using the app switcher. On iPad, the user can also display multiple instances of your app side by side. Each instance of your UI displays different content, or displays content in a different way. For example, the Calendar app can display the appointments for a specific day and for an entire month side by side.
UIKit manages each instance of your app's UI using a
UIWindow object. A scene contains the windows and view controllers you need to present one instance of your UI. Each scene also has a corresponding
UIWindow object, which you use to manage all interactions with the scene. Because scenes run concurrently with each other in the same memory and app process space, a single app may have multiple scenes and scene delegate objects that are active simultaneously. To manage your app's scenes, use a