Apache is a free and open-source cross-platform web server software.
Open Graph is a protocol that is used to integrate any web page into the social graph.
PHP is a general-purpose scripting language used for web development.
Site Kit is a one-stop solution for WordPress users to use everything Google has to offer to make them successful on the web.
Varnish is a reverse caching proxy.
Yoast SEO is a search engine optimisation plugin for WordPress and other platforms.