Apache is a free and open-source cross-platform web server software.
BookStack is a simple, open-source, self-hosted, easy-to-use platform for organising and storing information.
Debian is a Linux software which is a free open-source software.
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.