MariaDB is an open-source relational database management system that is a fork of MySQL. It was created to ensure continued development and support after concerns arose about MySQL's acquisition by Oracle Corporation. MariaDB is designed to be highly compatible with MySQL, making it easy for users to switch between the two. MariaDB offers various features, including improved performance, security enhancements, and a wide range of storage engines. It supports SQL (Structured Query Language) for managing and querying data, making it suitable for applications ranging from small websites to large enterprise systems.