Chatter is a standard feature that will be available on some record layouts to show a history of updates on the record and facilitate internal collaboration on a record.
From the Chatter Tab you can also see a feed of items related to you, add yourself to streams that are relevant to you or create new groups for targeted discussions.
Related Link: Chatter Basics Trailhead
Using Chatter via the desktop login:
Go to a Referral Record and access the Chatter Tab.
Enter a post and use the “@” feature to comment on another user in the system so they get a notification.
Access the Chatter Tab to see a feed of items related to you, add yourself to streams that are relevant to you or create new groups for targeted discussions.
Using Chatter via the mobile login:
From the mobile app, when you access a record you will see a link to chatter for that record if it’s available, you can click on it to see the record feed and contribute to the feed.