Apache is a free and open-source cross-platform web server software.
Calendly is an app for scheduling appointments, meetings, and events.
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.
PHP is a general-purpose scripting language used for web development.
RequireJS is a JavaScript library and file loader which manages the dependencies between JavaScript files and in modular programming.
YouTube is a video sharing service where users can create their own profile, upload videos, watch, like and comment on other videos.