MySQL is a relational database management system (RDBMS) that runs as a server providing multi-user access to a number of databases. SQL means Structured Query Language, which highlights its simplicity and ease of use. It is a declarative language as opposed to other procedural languages, what reduces the learning cycle from those that start in the language.
Various web applications uses MySQL databases, such as Joomla!, WordPress, MyBB, phpBB, Drupal and others. MySQL is also used in many high-profile, large-scale World Wide Web products, including Wikipedia, Google (though not for searches) and Facebook.