HTTP Strict Transport Security (HSTS) informs browsers that the site should only be accessed using HTTPS.
Open Graph is a protocol that is used to integrate any web page into the social graph.
RevolverMaps is a collection of real-time visitor statistics widgets for website or blog. Interactive visitor mappings to a globe rendered by the Revolver Engine.
Twitter is a 'microblogging' system that allows you to send and receive short posts called tweets.
YouTube is a video sharing service where users can create their own profile, upload videos, watch, like and comment on other videos.