AddThis is a social bookmarking service that can be integrated into a website with the use of a web widget.
Amazon Advertising (formerly AMS or Amazon Marketing Services) is a service that works in a similar way to pay-per-click ads on Google.
HTTP Strict Transport Security (HSTS) informs browsers that the site should only be accessed using HTTPS.
YouTube is a video sharing service where users can create their own profile, upload videos, watch, like and comment on other videos.