Starting, stopping and checking network services (systemctl status, ss -tlnp)

A network service is a daemon, a background program, that listens on a network port for clients: sshd on port 22, a web server on 80 and 443, chronyd for time. On RHEL, systemd manages daemons as service units, such as sshd.service or httpd.service, and systemctl is how you control them. A service task is only finished when the service is running now, will start at boot, and is actually listening where clients expect.