Definition of notification

A message or announcement sent to the user or administrator of a system. The recipient may be a human or an automated notification manager.

Information displayed to a user about someone else adding him or her to a contact list, a contact’s offline or online status, a missed conversation, voice mail message, service problem, or other item.

A message or other indicator that informs users of events that are unrelated to their current activity, such as the number of new messages received while their computer is locked.