When review information is marked up in the body of a web page, Google can identify it and use it to understand and present the information on your pages. Review information such as ratings and descriptions can help users to better identify pages with good content
The goal of a review rich snippet is to provide users with review information about a specific product or service, such as the star rating (1 to 5 stars) and the name of reviewer(s).
The following guidelines apply to review snippets:
When using review markup, the main topic of the page needs to be about a specific product or service. For example, using review markup on a page containing multiple products is not supported.
Review of adult-related products or services are not supported.
If the markup contains a single review, the reviewer’s name needs to be a valid name (Person or Organization). For example, "50% off until Saturday" is not a valid name for a reviewer.