The <meta> tag provides metadata about the HTML document

page-meta.html

Ref.: http://www.w3schools.com/tags/tag_meta.asp

<!-- for Google -->
<meta name="description" content="" />
<meta name="keywords" content="" />
<meta name="generator" content="" />
<meta name="author" content="" />
<meta name="copyright" content="" />
<meta name="application-name" content="" />

<!-- for Facebook -->          
<meta property="og:title" content="" />
<meta property="og:type" content="article" />
<meta property="og:image" content="" />
<meta property="og:url" content="" />
<meta property="og:description" content="" />

<!-- for Twitter -->          
<meta name="twitter:card" content="summary" />
<meta name="twitter:title" content="" />
<meta name="twitter:description" content="" />
<meta name="twitter:image" content="" />