I ran for var in $(systemctl | grep running | awk '{print $1}'); do systemctl status $var | grep "changed on disk" | grep ".service"; done to see what files had been changed, out of curiosity, and found dhcpcd.service getty@tty1.service systemd-timesyncd.servi...
An example could be a dhcpcd@.service service template which takes a network interface as a parameter to form an instantiated service. Within the service file, this parameter or "instance name" can be accessed with %-specifiers. See systemd.unit(5) for details. AUTOMATIC DEPENDENCIES...