# systemctl list-units --state=running --type=service
UNIT                      LOAD   ACTIVE SUB     DESCRIPTION
accounts-daemon.service   loaded active running Accounts Service
acpid.service             loaded active running ACPI event daemon
atd.service               loaded active running Deferred execution scheduler
[email protected]       loaded active running Ceph object storage daemon osd.17
cron.service              loaded active running Regular background program processing daemon
dbus.service              loaded active running D-Bus System Message Bus
[email protected]        loaded active running Getty on tty1
iscsid.service            loaded active running iSCSI initiator daemon (iscsid)
lvm2-lvmetad.service      loaded active running LVM2 metadata daemon
lxcfs.service             loaded active running FUSE filesystem for LXC
mdadm.service             loaded active running LSB: MD monitoring daemon
polkitd.service           loaded active running Authenticate and Authorize Users to Run Privileged Tasks
rsyslog.service           loaded active running System Logging Service
ssh.service               loaded active running OpenBSD Secure Shell server
systemd-journald.service  loaded active running Journal Service
systemd-logind.service    loaded active running Login Service
systemd-timesyncd.service loaded active running Network Time Synchronization
systemd-udevd.service     loaded active running udev Kernel Device Manager
[email protected]         loaded active running User Manager for UID 1000

LOAD   = Reflects whether the unit definition was properly loaded.
ACTIVE = The high-level unit activation state, i.e. generalization of SUB.
SUB    = The low-level unit activation state, values depend on unit type.

19 loaded units listed. Pass --all to see loaded but inactive units, too.
To show all installed unit files use 'systemctl list-unit-files'.