Meta Tag Information
Meta tags provide additional information about a web page. They are hidden html tags, but provide search engines with useful information needed to analyze, categorize and rank your web page. These should be limited to 150-160 characters. Proper use of the meta tags can substantially increase your search engine traffic to your website.
Open Graph Protocol Tag Information
Similar to meta tags, the Open Graph protocol enables any web page to become a rich object in a social graph. For instance, this is used on Facebook to allow any web page to have the same functionality as any other object on Facebook.