The Approval review option enables you to send content for a formalized approve-or-reject type review. Reviewers must choose to either approve or reject each topic in the review. If they suggest changes to a topic, the topic is rejected and goes to an Editorial release state in order to incorporate suggested changes.
An Approval review also enables an authorized reviewer to "sign-off" the content for release if it has been approved by an approver. The sign-off is not a digital signature but a recorded event change in the history of the object. This enables the sign-off to be retrieved in the future if necessary.