[Nut-upsuser] What is a "configure-file device"?

[Roger Price]

The command "systemctl status nut-driver-enumerator" in my 2.7.4 installation 
returns:

● nut-driver-enumerator.service - Network UPS Tools - enumeration of
   configure-file devices into systemd unit instances
      Loaded: loaded (/lib/systemd/system/nut-driver-enumerator.service;
   disabled; vendor preset: enabled)
      Active: inactive (dead)

What is a "configure-file device"? Do I need it?  When, if ever, does this 
service unit get run?

Roger