Meta descriptions are HTML attributes that provide concise explanations of the contents of web pages. Meta descriptions are commonly used on search engine result pages (SERPs) to display preview snippets for a given page.
Sites who has this tag are verfied by google to use WebMaster tools
The http-equiv attribute provides an HTTP header for the information/value of the content attribute. The http-equiv attribute can be used to simulate an HTTP response header.
Indicates that the site provides an interface specifically for searching the document and its related resources.
A canonical link element is an HTML element that helps webmasters prevent duplicate content issues by specifying the "canonical", or "preferred".
Meta Keywords are a specific type of meta tag that appear in the HTML code of a Web page and help tell search engines what the topic of the page is.