A subscription is the link between an alert and an employee to whom you wish the alert to be delivered. Users who subscribe, or who are subscribed by others to an alert, receive alert notifications when specific business objects are in an alert state and require attention.
Creating an alert and a subscription can be performed separately, although you can both create and subscribe to an alert in one step.
All users can subscribe themselves to a public alert. However, only users with the admin security role can create public alerts to which they subscribe other users.
Users can unsubscribe from any alert, including those to which an administrator has subscribed them. If the administrator does not want users to unsubscribe from a particular alert, it can be locked.