jQuery CDN is a way to include jQuery in your website without actually downloading and keeping it your website's folder.
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.
Microsoft Ajax Content Delivery Network hosts popular third party JavaScript libraries such as jQuery and enables you to easily add them to your web applications.
Nginx is a web server that can also be used as a reverse proxy, load balancer, mail proxy and HTTP cache.
Pure CSS is a set of small, responsive CSS modules that can be used in web projects.
Unpkg is a content delivery network for everything on npm.