Every MySQL is shipped with default system schemas/databases. Those are:

• mysql - is the system database that contains tables that store information required by the MySQL server
• information_schema - provides access to database metadata
• performance_schema - is a feature for monitoring MySQL Server execution at a low level
• sys - a set of objects that helps DBAs and developers interpret data collected by the Performance Schema

Please note that some database tools hide system schemas by default. Using MySQL Workbench for instance you will not see them in the Object Browser unless you change settings. However, you have access to those schemas and you can query tables and views right away. For instance:

select * from information_schema.tables