Who doesn’t know those beautiful stars that Google shows on the search result page with some websites. The increases the size of your listing in the search engine result page (SERP) and the stars that are showing will increase the click through rate (CTR) of your listing!
The Reviewer Rich Snippets plugin will automatically add the schema.org markup to your review that Google requires to show the ratings on the SERPs.
The extension adds the structured data, ultimately Google decides with who to show the rich snippets.
You can read more about the introduction to structured data by Google.