AddThis is a social bookmarking service that can be integrated into a website with the use of a web widget.
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.
Pinterest is an image sharing and social media service designed to enable saving and discovery of information.
Twitter is a 'microblogging' system that allows you to send and receive short posts called tweets.