If you use a script-driven app for your website, any info that both you and the site users generate shall be stored within a database - a collection of info, that's structured in cells and tables for simplier and easier reading and writing. The latter is carried out by using special software called database management system and one of the most widely used ones globally is MySQL. A large amount of script apps are designed to work with MySQL as it's simple to use, it functions exceptionally well on a hosting server and it is universal as it can perform with widely used web programming languages (Python, Perl, PHP, Java) and on several web server OS (Windows, Linux, UNIX). There are thousands of scripts which use MySQL, including popular ones like WordPress, Joomla and Moodle.