When you check the Expect Customer Reply option in your response, a copy of your answer is placed in this list. You can send follow-up requests from this page, and your requests will quote your original answer. When the contact replies to your agent response, their question will be automatically assigned to you and your pending message will be removed from the list.
The page looks and functions identically to the My Message Inbox, except it is a list of your answers instead of customer questions.