Apple Sign-in is based on OAuth 2.0 and OpenID Connect, and provides a privacy-friendly way for users to sign in to websites and apps.
cdnjs is a free distributed JS library delivery service.
HTTP Strict Transport Security (HSTS) informs browsers that the site should only be accessed using HTTPS.
Linkedin Ads is a paid marketing tool that offers access to Linkedin social networks through various sponsored posts and other methods.
Twitter is a 'microblogging' system that allows you to send and receive short posts called tweets.