MariaDB and MySQL are both open source relational database management systems (RDBMS). They are both based on the same SQL language and have similar features.
The main difference between MariaDB and MySQL is that MariaDB is a fork of MySQL, meaning that it was created from the same source code as MySQL. MariaDB was created by the original developers of MySQL and is now maintained by the MariaDB Foundation.
MariaDB also has some additional features that MySQL does not have, such as support for more storage engines, more security features, and more performance enhancements. Additionally, MariaDB is more actively developed than MySQL, meaning that it is more likely to have the latest features and bug fixes.