What is Replication slots in PostgreSQL Streaming

WAL accumulating, Logical Replication pg 13 error_ replication slot is active for pid logical replication worker exited with exit code 1 I did see this error message before and my process was to increase error 1089 slot_name my_pub1 plugin pgoutput slot_type logical datoid 16401 database db temporary f active t active_pid

error_ replication slot is active for pid replication slot started lagging