cdnjs is a free distributed JS library delivery service.
Facebook pixel is an analytics tool that allows you to measure the effectiveness of your advertising.
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.
Tippy.js is the complete tooltip, popover, dropdown, and menu solution for the web, powered by Popper.
Unpkg is a content delivery network for everything on npm.