Facebook pixel is an analytics tool that allows you to measure the effectiveness of your advertising.
Google Publisher Tag (GPT) is an ad tagging library for Google Ad Manager which is used to dynamically build ad requests.
Google Sign-In is a secure authentication system that reduces the burden of login for users, by enabling them to sign in with their Google account.
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.
reCAPTCHA is a free service from Google that helps protect websites from spam and abuse.
YouTube is a video sharing service where users can create their own profile, upload videos, watch, like and comment on other videos.