cdnjs is a free distributed JS library delivery service.
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.
Modernizr is a JavaScript library that detects the features available in a user's browser.
Open Graph is a protocol that is used to integrate any web page into the social graph.
Plyr is a simple, lightweight, accessible and customizable HTML5, YouTube and Vimeo media player that supports modern browsers.
Progressive Web Apps (PWAs) are web apps built and enhanced with modern APIs to deliver enhanced capabilities, reliability, and installability while reaching anyone, anywhere, on any device, all with a single codebase.