pg_description

The pg_description system catalog table stores optional descriptions (comments) for each database object. Descriptions can be manipulated with the COMMENT command and viewed with psql's \d meta-commands. Descriptions of many built-in system objects are provided in the initial contents of pg_description. See also pg_shdescription, which performs a similar function for descriptions involving objects that are shared across a Greenplum system.

column	type	references	description
objoid	oid	any OID column	The OID of the object this description pertains to.
classoid	oid	pg_class.oid	The OID of the system catalog this object appears in
objsubid	integer		For a comment on a table column, this is the column number. For all other object types, this column is zero.
description	text		Arbitrary text that serves as the description of this object.

Parent topic: System Catalogs Definitions