Notification center is a MECHANISM that allows the publisher of knowledge to registered observers. Objects register with a notification center to receive notifications (NSNotification objects). Once associate object adds itself as an assistant observer, it specifies that notifications it ought to receive. The associate object might, therefore, the decision this methodology many times so as to register itself as an associate observer for many totally different notifications. Local notifications and remote notifications square measure ways that to tell users once new knowledge becomes on the market for your app, even once your app isn't running within the foreground. For instance, an electronic communication app would possibly let the user apprehend once a replacement message has arrived, associated a calendar app would probably inform the user of an impending appointment. The DISTINCTION between native and remote notifications is straightforward:

• With native notifications, your app configures the notification details REGIONALLY and passes those details to the system that then handles the delivery of the information once your app isn't within the foreground. Native notifications square measure supported on iOS, tvOS, and watchOS.
• With remote notifications, you utilize one AMONGST your company’s servers to push knowledge to user devices via the Apple Push Notification SERVICE. Remote warnings square measure supported on iOS, tvOS, watchOS, and macOS.