what is a .new file and where is it explained in csf docs?

[bulgin23]

Whenever csf updates it produces an output like:

‘csf.blocklists’ -> ‘/etc/csf/csf.blocklists.new’

this is totally confusing. If it's "new" that would imply it is replacing the "old" file. Yet, how can it be new AND functional if it's labelled something like "csf.blocklists.new"

Are we to assume the old (not "new") is still in use?

Or, is .new the new "new"?

Totally confusing and without any explanation that I can find anywhere.

[Sergio]

The file "csf.blocklists.new" is created when for the first time CSF is installed on your server.
It is not used for anything else after that.