Fastly is a cloud computing services provider. Fastly's cloud platform provides a content delivery network, Internet security services, load balancing, and video & streaming services.
GitHub Pages is a static site hosting service.
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.
Tidio is a customer communication product. It provides multi-channel support so users can communicate with customers on the go. Live chat, messenger, or email are all supported.
Varnish is a reverse caching proxy.