pgclass
pg_class is a system catalog relation in PostgreSQL that stores metadata for every relation in a database. It resides in the pg_catalog schema and is one of the core catalogs used to describe database objects. Each row represents a relation, which can be a regular table, index, sequence, view, materialized view, partitioned table, foreign table, or a TOAST-related object. The object identifier (oid) uniquely identifies the row; other fields provide the object's name (relname), its namespace (relnamespace), and its owner (relowner). The relkind column encodes the kind of relation, with common codes such as r for ordinary tables, i for indexes, S for sequences, v for views, m for materialized views, f for foreign tables, t for TOAST tables, and p for partitioned tables.
Other important fields capture storage and statistics. reltablespace indicates the tablespace for the relation’s files, relpages
Usage and interpretation: pg_class is queried to inspect catalog metadata and is often joined with pg_namespace