Chatter feed tracking
Key Takeaway
When a tracked field changes, Salesforce posts an update to the record's Chatter feed. Users who follow the record must have access to it to see the update.
Feed tracking lets you pick record fields to watch, so people who follow a record can see important changes without opening it. Admins choose which objects and fields to track, starting from a set of defaults.
Tracked updates and who sees them
Feed tracking detects changes to tracked record fields and posts them to the record's Chatter feed as tracked updates.
For example, imagine that an account gets a new owner. A system message noting the change appears on the account's feed.
Users who follow a record see its tracked updates in their "What I Follow" feed. The one exception is a user's own changes: those updates don't appear in that user's What I Follow feed, but they do appear in the user's profile feed.
Sharing rules and field-level security decide who sees tracked updates in Chatter feeds. A user must have access to a record to see its tracked updates in their feed. Following a record does not show changes the user can't otherwise access.