Magento is an open-source content management system for e-commerce web sites. The software was originally developed by Varien Inc., a US private company headquartered in Los Angeles, with assistance from volunteers.
PHP is a server-side scripting language designed for web development but also used as a general-purpose programming language.
MySQL is a popular choice of database for use in web applications, and is a central component of the widely used LAMP open source web application software stack (and other 'AMP' stacks). LAMP is an acronym for "Linux, Apache, MySQL, Perl/PHP/Python." Free-software-open source projects that require a full-featured database management system often use MySQL.
XHTML (Extensible HyperText Markup Language) is a family of XML markup languages that mirror or extend versions of the widely used Hypertext Markup Language (HTML), the language in which Web pages are written.