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.
The Tweet Button is a small widget which allows visitors to share content and connect on Twitter.
Open graph description entity tag
A WebSite is a set of related web pages and other items typically served from a single web domain and accessible via URLs.
Sites who has this tag are verfied by google to use WebMaster tools