pg_extension stores information about the installed extensions. See Section 38.17 for details about extensions.
Name of the extension
Owner of the extension
Schema containing the extension's exported objects
True if extension can be relocated to another schema
Version name for the extension
Note that unlike most catalogs with a “namespace” column,
extnamespace is not meant to imply that the extension belongs to that schema. Extension names are never schema-qualified. Rather,
extnamespace indicates the schema that contains most or all of the extension's objects. If
extrelocatable is true, then this schema must in fact contain all schema-qualifiable objects belonging to the extension.