Approval Workflow gives outreach managers an opportunity to directly oversee the activity of their team. When this feature is enabled, the head of an outreach team has the ability to accept (send) or reject opportunities sitting in the Compose stage of the workflow. Rejected opportunities will be sent back to 'Personalize'.
To learn how to turn on Approval Workflow, see: Campaign Settings: General
When rejecting an opportunity, the outreach manager is given the option to leave notes for the team members to view the next time they log in, explaining the reason for the rejection.