Bootstrap is a free and open-source CSS framework directed at responsive, mobile-first front-end web development. It contains CSS and JavaScript-based design templates for typography, forms, buttons, navigation, and other interface components.
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.
Headroom.js is a JS widget that allows you to react to the user's scroll. The header slides out of view when scrolling down and slides back in when scrolling up.
HTTP Strict Transport Security (HSTS) informs browsers that the site should only be accessed using HTTPS.
Popper is a positioning engine, its purpose is to calculate the position of an element to make it possible to position it near a given reference element.
Varnish is a reverse caching proxy.