Rich snippets
Rich Snippets enhance a search result with additional information. Rich Snippets are for example breadcrumbs, photos, event information or rating stars which are displayed underneath a search result.
In order to display the rating stars as Rich Snippets, search engines must be able to obtain and interpret relevant information: structured data. To make your pages eligible for Rich Snippets in search results, add structured data to the source code of your website by using a specific vocabulary (schema.org), that all the major search engines comply with.

What is SEO?
SEO stands for Search Engine Optimization, and includes the organic (unpaid) results from search engines. SEO consists in following certain rules and techniques in order for a website to obtain a good ranking in search results after having been analysed by a search engine.
Why bother with SEO stars?
Rich snippets effectively contribute to search engine optimization. The displayed stars are a real eye-catcher: they attract the user’s attention to a particular search result which will thereby be clicked on more often. Results with high click rates are in turn classified by search engines as particularly relevant for the searcher. This serves to positively influence the ranking of the website in question. A better ranking means more visitors on the website. More visitors means more clients and more clients means more customer reviews.