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.
Google AdSense is a program run by Google through which website publishers serve advertisements that are targeted to the site content and audience.
Google Analytics is a free web analytics service that tracks and reports website traffic.
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.
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.
PayPal is an online payments system that supports online money transfers and serves as an electronic alternative to traditional paper methods like checks and money orders.
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.