Though Google doesn’t release details about its algorithm for Search Engine Optimization (SEO), many SEO experts believe that having reviews on your website can help you to move up the search results. Having star ratings also increases "search engine results page click-through-rate" (SERP CTR), which indirectly improves your organic rank.
The Review Display Widget uses “schema.org markup” which is supported by Google “structured data”. This is a standard for how you label data on your website so that browsers and search engines can interpret it and know what it represents. This means that it can identify that a review on your site is actually a review.
The widget is also set up so that the “Aggregate Rating” data is included in the number of reviews and the average rating. This is how Google knows what star rating to include in their search results. Of course, you can’t guarantee that the star rating will appear in the search results since that is up to Google but we have done everything we can to make it possible to show up.