Rich snippets provide webmasters with the ability to add useful information to their web search results and present users with more information on the content of the website. Rich snippets mark-up must accurately reflect the primary content of the page.
Rich snippet mark-up on the site also allows Google to better understand structured nature of data on the page and is particularly useful for database driven web sites showing structured data like products, recipes, names and addresses, events etc.
Three formats are supported namely microdata, microformats, or RDFa.
Recent results also show that a structured list with defined class attributes are included in Snippets as a bullet list with the first 3 records shown e.g.
- 01 23 4567 890
See Google Webmaster Tools Help for more information on this.
See also - Snippets