LiveAgent offers you to add private notes to a ticket that are only visible to agents, not to the ticket requester or any other end-users that may have been CC'd on the ticket. This enables you to share progress internally, or log your updates for future reference. You can even transfer the ticket with an internal note to another agent.
Example Your customer explained an issue in six long emails, you can summarize this issue in a note and transfer it to the developers who will handle and solve it. They don’t have to read all the emails from the customer (that would be time-wasting), your summary of the issue in the added note is sufficient for them.