Apple Push Notification server open to developers
9to5mac.com/2009/04/09/apple-push-notification-server-open-to-developers
From the page
Saved with the link. Notes from 2007 to 2016 are mostly the page's own words, so this is probably an excerpt.
Apple told developers today that their Push Notification servers were ready for testing. Those developers whose application hope to operate behind the scenes will need to use this service to notify users of new information.