The Review/Rating Feature can be turned on and off in the Configuration. There you can also set if reviews are automatically published or must be moderated before being published. Only registered Customers can submit Ratings and Reviews - and only one per Product.
You can access the list of all Reviews for a Product from the Product List, Column "Customer Reviews". If a Product jas no Review yet, the link says "Add a Review", which brings you to the Review Form, where you can add Reviews.
If a Product has one or more Reviews, you can view the List of all Reviews.
To edit or view a Review click on the user name in the "Name" Column - this will bring you to the Review Form.
You can quickly (un)publish a Review by clicking the Icon in the "Publish" Column. To completely remove a Review, you can click the Trash Icon in the last Column or select on or more Reviews and click "Remove" in the Toolbar.