From the manual:
systemd, init - systemd system and service manager
systemd is a system and service manager for Linux operating systems. When run as first process on boot (as PID 1),
it acts as init system that brings up and maintains userspace services.
For compatibility with SysV, if systemd is called as init and a PID that is not 1, it will execute telinit and
pass all command line arguments unmodified. That means init and telinit are mostly equivalent when invoked from
normal login sessions. See telinit(8) for more information.
When run as system instance, systemd interprets the configuration file system.conf, otherwise user.conf. See
systemd-system.conf(5) for more information.
Simply put, sysyemd is like system v init, only much, much better, more logical, more user friendly.
I wonder why wasn't there ever a "boycott upstart" action, when upstart is million times worse than systemd.