A pingback is one of four types of linkback methods for Web authors to request notification when somebody links to one of their documents. This enables authors to keep track of who is linking to, or referring to their articles.
nginx [engine x] is a HTTP server and mail proxy server written by Igor Sysoev.
Open graph description entity tag
Open graph title entity tag
A canonical link element is an HTML element that helps webmasters prevent duplicate content issues by specifying the "canonical", or "preferred".