Facebook pixel is an analytics tool that allows you to measure the effectiveness of your advertising.
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.
reCAPTCHA is a free service from Google that helps protect websites from spam and abuse.
VK is a Russian online social media and social networking service.
YouTube is a video sharing service where users can create their own profile, upload videos, watch, like and comment on other videos.