MySQL is a relational database management system (RDBMS). MySQL is popular for web applications and acts as the database component of the LAMP platform (Linux-Apache-MySQL-PHP/Perl/Python).
Its popularity for use with web applications is closely tied to the popularity of PHP and Ruby on Rails, which are often combined with MySQL.
PHP and MySQL are essential components for running popular content management systems such as Expression Engine, Drupal, Joomla! and WordPress.
Several high-traffic web sites use MySQL for its data storage and logging of user data, including Flickr, Facebook, Wikipedia and YouTube.