Apple Push Notification Services

The Apple Push Notification Service is a mobile service created by Apple Inc. that was released with iOS It uses push technology through a constantly-open IP connection to forward notifications from the servers of third party applications to the iPhone or iPod Touch and now the iPad; such notifications may include badges, sounds or custom text alerts. To get more details, Please follow the below mentioned links:

http://mobiforge.com/developing/story/programming-apple-push-notification-services

For othere more information Just copy & paste below link in your browser address bar: 

http://developer.apple.com/library/ios/#documentation/

NetworkingInternet/Conceptual/RemoteNotificationsPG/

ApplePushService/ApplePushService.html