HTTP Strict Transport Security (HSTS) informs browsers that the site should only be accessed using HTTPS.
Open Graph is a protocol that is used to integrate any web page into the social graph.
Phusion Passenger is a free web server and application server with support for Ruby, Python and Node.js.
Progressive Web Apps (PWAs) are web apps built and enhanced with modern APIs to deliver enhanced capabilities, reliability, and installability while reaching anyone, anywhere, on any device, all with a single codebase.
Ruby on Rails is a server-side web application framework written in Ruby under the MIT License.
Varnish is a reverse caching proxy.