Users register interest in the Chatter activity of a record by clicking Follow icons in the Force.com user interface or by automatically following owned records. Users can follow other users as well as records in standard and custom objects. The information about followers is prominently displayed throughout the standard user interface, and used to email digests and notifications to users if Chatter is configured to do so.
All of this functionality hinges upon a single, simple object, called
EntitySubscription. Its two important fields are
ParentId, the record being followed, and
SubscriberId, the Id of the user doing the following. For every record-to-user relationship in the organization, a unique record in