Yup, basically. Systemd is "the first program" that runs, and then its job is to start all the other programs that make up a modern computer, most of which run in the background and a user will never see. It's not the only such "init program", though, and some people are grumpy that it does too much itself, rather than simply starting other programs to do those things.

But unless you're involved in starting and stopping background processes, you can't really tell which one you've got. Users aren't "meant" to care which process was the one that started the power management daemon, or whatever.