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.
The lite-youtube-embed technique renders the YouTube video inside the IFRAME tag only when the play button in clicked thus improving the core web vitals score of your website.
Nginx is a web server that can also be used as a reverse proxy, load balancer, mail proxy and HTTP cache.
Open Graph is a protocol that is used to integrate any web page into the social graph.
Varnish is a reverse caching proxy.