Apache is a free and open-source cross-platform web server software.
Contao is an open source CMS that allows you to create websites and scalable web applications.
HTTP Strict Transport Security (HSTS) informs browsers that the site should only be accessed using HTTPS.
OpenSSL is a software library for applications that secure communications over computer networks against eavesdropping or need to identify the party at the other end.
PHP is a general-purpose scripting language used for web development.
Unix is a family of multitasking, multiuser computer operating systems.