Incremental View Maintenance (IVM) provides a method for keeping materialized views current by calculating and applying only the incremental changes, as opposed to the complete recomputation of contents performed by the REFRESH MATERIALIZED VIEW command.
Materialized View in PostgreSQL
A materialized view is a database object that stores the result set of a query as a physical table, persisting the computed data for improved query performance. In contrast to regular views, materialized views contain actual data rather than merely defining a query.