pg_description stores optional descriptions (comments) for each database object. Descriptions can be manipulated with the COMMENT command and viewed with psql's
\d commands. Descriptions of many built-in system objects are provided in the initial contents of
pg_shdescription, which performs a similar function for descriptions involving objects that are shared across a database cluster.
The OID of the object this description pertains to
The OID of the system catalog this object appears in
For a comment on a table column, this is the column number (the
Arbitrary text that serves as the description of this object