nginx [engine x] is a HTTP server and mail proxy server written by Igor Sysoev.
Sites who has this tag are verfied by google to use WebMaster tools
Chrome for Android, since version 39 supports the "theme-color" meta tag to allow websites control the background color of the tab's UI header.
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.