Social Meta Reference
There are a variety of social tags that can be implemented for integration with each of the social networks. Some tags are used by multiple social networks, like Open Graph, while others are specific to only one social network, like Twitter Cards.
Open Graph tags are arguably the most important tags to implement on your site. These tags are used by Facebook, LinkedIn and Google+ for enhancing any shared content, which means that adding just a few tags to your site can help you to control your presence and branding on these social networks.View items...
Twitter Cards are social meta tags specific to Twitter. These tags create 'cards' that are shown alongside any Tweets that you're site is included in. If you are at all targeting Twitter or think your content may be shared, you should be adding these tags. Please note: For Twitter to include a 'card' for your site, you must first be approved.View items...
Schema.org Microdata is inline syntax used anywhere in the body section of your site to denote the title, description, image, type of page and other information. Microdata can be more complex to add since it's done inline, which means you may have to make modifications to whatever generates your page's output.
Schema.org Microdata is used by multiple search engines as well as Google+.View items...