Rich snippets are like tools used by webmasters which can structure your website data and present it to search engines. There are various rich snippets available for you to use. It is just one way to distinguish your website from others and creating its own identity for search engines. Google uses this snippet data to rank your website for the most relevant queries. You can format your website with star ratings, reviews, author, article images etc. know more about it here: http://wordpress.org/plugins/all-in-one-schemaorg-rich-snippets/