You can use Content rating to allow live site users to rate any document on your website, for example, if you want your website users to express their opinion about the quality of content. Content rating has no dedicated user interface - the overall rating of each document appears in the Rating field on the General tab in a document's Properties.
Enable content rating by placing the Content rating web part on a page. See Using the Content rating web part for more details.
You can also include a rating control in transformations to enable users to rate each transformed item. See Displaying content rating in transformations.
The content rating functionality is also integrated in web parts belonging to the Message boards application. This enables live site users to submit a rating along with a comment posted to the message board. To learn more, see Using content rating in message boards.