Metadata in a database refers to data that describes the structure, contents, and context of the database. It is "data about data."
Metadata can include information such as the names and types of tables and columns, relationships between tables, constraints on data, indexes, views, and other database objects. It can also include information about the source and history of the data, such as when it was created, who created it, and how it was modified.
Metadata is used by the database management system (DBMS) to understand the structure and contents of the database, and to optimize the performance of queries and other operations. It is also used by database administrators and developers to maintain and manage the database, and by users to understand the data and its context.