jQuery CDN is a way to include jQuery in your website without actually downloading and keeping it your website's folder.

Cloudflare is a web-infrastructure and website-security company, providing content-delivery-network services, DDoS mitigation, Internet security, and distributed domain-name-server services.

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.

PHP is a general-purpose scripting language used for web development.

JSDelivr is a free public CDN for open-source projects. It can serve web files directly from the npm registry and GitHub repositories without any configuration.

Nginx is a web server that can also be used as a reverse proxy, load balancer, mail proxy and HTTP cache.

jQuery is a JavaScript library which is a free, open-source software designed to simplify HTML DOM tree traversal and manipulation, as well as event handling, CSS animation, and Ajax.

cdnjs is a free distributed JS library delivery service.

Varnish is a reverse caching proxy.