MyISAM was the default storage engine from MySQL 3.23 until it was replaced by InnoDB in MariaDB and MySQL 5.5. It's a light, non-transactional engine with great performance, is easy to copy between systems and has a small data footprint.

You're encouraged to rather use the Aria storage engine for new applications, which has even better performance and the goal of being crash-safe.

Until MariaDB 10.4, system tables used the MyISAM storage engine.