MySQL is the world's most popular and most used open source relational database management system. With its proven performance, reliability and ease-of-use, MySQL has become the leading database choice for web-based applications, used by high profile web properties including Facebook, Twitter, YouTube, Yahoo! and many more. The SQL phrase stands for Structured Query Language and is an essential part of almost every open source PHP application. Good examples for PHP/MySQL-based scripts are phpBB, Joomla and WordPress.
The most common use for MySQL is for the purpose of a web database. It can be used to store anything from a single record of information to an entire inventory of available products for an online store.
MySQL has one major advantage. Since it is free, it is usually available on shared hosting packages and can be easily set up in a Linux, Unix or Windows environment. If a web application requires more than a database, such as load balancing, it is easy to set up. MySQL is also an open-source product meaning many independent developers work on the code without monetary compensation. This means updates and fixes are readily available from the community and many companies offer commercial support for MySQL.