All script applications such as forums or virtual stores store their data in a database - a group of cells and tables which contains the website info like items, prices, comments, and many others. Every time you open a certain page, the script connects to the database and retrieves the necessary information, then shows it. The intermediary software which connects the script and the database is referred to as a database management system and one of the most widely used ones is MySQL. The latter is frequently used simply because it runs on various platforms (Windows, Linux, UNIX) and with numerous scripting languages (PHP, Java, Python, Perl), not mentioning its amazing performance even with big databases. A lot of popular platforms including Joomla™ or WordPress employ MySQL databases to keep their content.