cdnjs is a free distributed JS library delivery service.

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

Google Hosted Libraries is a stable, reliable, high-speed, globally available content distribution network for the most popular, open-source JavaScript libraries.

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.

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.

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

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.

BootstrapCDN is a powerful and reliable Content Delivery Network (CDN) that delivers static resources, including CSS, JavaScript, and font files, for the widely-used Bootstrap framework. By leveraging multiple server locations worldwide, BootstrapCDN accelerates website loading times, ensuring a smooth and visually appealing user experience. Additionally, it ensures website compatibility with various devices and browsers. The service reduces bandwidth usage and server load, improving web performance for developers and end-users alike.

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

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

Varnish is a reverse caching proxy.