What is the effect of using Google Snippets?

Rich Snippets. Rich snippets are search results that go beyond the basics. They are, by definition, a richer result than the ordinary. Using structured data markup (more on that in a moment) added to your site HTML, you provide the search engines more information to better understand the content and intent of each page

Rich Snippets is the term used to describe structured data markup that site operators can add to their existing HTML, which in turn allow search engines to better understand what information is contained on each web page.