Hive Metastore is a data storage layer that stores the structure of the data in a Hive warehouse. It acts as a central repository for metadata and also helps in providing access to external tools that need to access the Hive tables.
While MySQL Metastore is a type of database that is used to store Hive data such as table definitions, partitions, and statistics. Additionally, MySQL Metastore provides an interface to users to manage, query, and access the data stored in the Hive warehouse, while Hive Metastore does not have this capability.