pg_shdescription stores optional descriptions (comments) for shared database objects. Descriptions can be manipulated with the COMMENT command and viewed with psql's
pg_description, which performs a similar function for descriptions involving objects within a single database.
Unlike most system catalogs,
pg_shdescription is shared across all databases of a cluster: there is only one copy of
pg_shdescription per cluster, not one per database.
The OID of the object this description pertains to
The OID of the system catalog this object appears in
Arbitrary text that serves as the description of this object