How is the user informed about events when the application is inactive or closed?

When an iOS app is inactive or closed, the user is informed about events through local or push notifications.

Push notifications are sent from the server via the Apple Push Notification service (APNs) and appear in the notification center, on the lock screen, or as a banner. They help attract the user's attention even if the app is not running.

Local notifications are created by the app itself and scheduled for a specific time or event, and also appear in the notification system.

Thus, the main way to inform the user outside of the app's activity is through notifications displayed by the iOS system.