Once the review is completed, user could decide to approve or reject the product data, either from the content header

Or at the end of the page.

By clicking "Approve", the product data will be approved and sync to related sales channel.

And if the product data has any problem and user would like to reject, they could click on "Reject" button. During the product rejection, user could leave message to indicate the problem and let seller amend the data

For seller to view the comment, please refer to this article