What is the dump.rdb in the nodebb root dir?

[Ken OKABE]

According to the docs,
https://docs.nodebb.org/en/latest/upgrading/index.html

On typical installs of Redis, the main database is found at
/var/lib/redis/dump.rdb.

and the file actually is there.

So, what is the dump.rdb in the nodebb root dir?

Thanks.