PostgreSQL Documentation: archive_mode parameter
When archive_mode is enabled, completed WAL segments are sent to archive storage by setting archive_command. In addition to off, to disable, there are two modes: on, and always. During normal operation, there is no difference between the two modes, but when set to always the WAL archiver is enabled also during archive recovery or standby mode.
https://postgresqlco.nf/doc/en/param/archive_mode/