facebook - https://developers.facebook.com/docs/sharing/best-practices#tags
<meta property="og:title" content="Facebook Open Graph META Tags"/>
<meta property="og:image" content="http://example.com/assets/img/logo_for_facebook.png"/>
<meta property="og:site_name" content="Some Awesome Website"/>
<meta property="og:description" content="Facebook's Open Graph protocol allows for web developers to turn their websites into Facebook "graph" objects, allowing a certain level of customization over how information is carried over from a non-Facebook website to Facebook when a page is 'recommended', 'liked', or just generally shared."/>twitter cards
https://dev.twitter.com/cards/types
<meta name="twitter:card" content="summary_large_image">
<meta name="twitter:site" content="@nytimes">
<meta name="twitter:creator" content="@SarahMaslinNir">
<meta name="twitter:title" content="Parade of Fans for Houston’s Funeral">
<meta name="twitter:description" content="NEWARK - The guest list and parade of limousines with celebrities emerging from them seemed more suited to a red carpet event in Hollywood or New York than than a gritty stretch of Sussex Avenue near the former site of the James M. Baxter Terrace public housing project here.">
<meta name="twitter:image:src" content="http://graphics8.nytimes.com/images/2012/02/19/us/19whitney-span/19whitney-span-articleLarge.jpg">