The mysql.component sytem table contains information about currently loaded components and shows which components have been registered using INSTALL COMPONENT. Selecting from the table shows which components are installed. For example:

mysql> SELECT * FROM mysql.component;
+--------------+--------------------+------------------------------------+
| component_id | component_group_id | component_urn                      |
+--------------+--------------------+------------------------------------+
|            1 |                  1 | file://component_validate_password |
|            2 |                  2 | file://component_log_sink_json     |
+--------------+--------------------+------------------------------------+

The component_id and component_group_id values are for internal use. The component_urn is the URN used in INSTALL COMPONENT and UNINSTALL COMPONENT statements to load and unload the component.