CSS, (Cascading Style Sheets) is a style sheet language used to describe the presentation semantics (the look and formatting) of a document written in a markup language (HyperText Markup Language), designed primarily to improve content accessibility, provide more flexibility and control in the specification of presentation characteristics, enable multiple pages to share formatting, and reduce complexity and repetition in the structural content (such as by allowing for tableless web design)...

PHP, (PHP: Hypertext Preprocessor) is a general-purpose scripting language originally designed for web development to produce dynamic web pages. PHP code is embedded into the HTML source document and interpreted by a web server, which generates the web page document. PHP can be deployed on most web servers and on almost every operating system and platform free of charge. A competitor to Microsoft's Active Server Pages (ASP) (my favorite part) and similar languages, PHP is installed on more than 20 million websites and 1 million web servers.

MySQL, (developer Michael Widenius' daughter, My, Structured Query Language) is a relational database management system (RDBMS) that runs as a server providing multi-user access to a number of databases. Projects that require a full-featured database management system often use MySQL. Applications which use MySQL databases include: Joomla, WordPress, phpBB, Drupal and other software built on the LAMP software stack. MySQL is also used in many high-profile, large-scale World Wide Web products, including Wikipedia, Google and Facebook.