I was wondering why does “cat /etc/group” show both groups and users?
I mean shouldn’t it show only group?
How do I recognize if it’s a group or a user?

cat /etc/group
root:x:0:
bin:x:1:
daemon:x:2:
sys:x:3:
adm:x:4:
tty:x:5:
disk:x:6:
lp:x:7:
mem:x:8:
kmem:x:9:
wheel:x:10:
cdrom:x:11:
mail:x:12:postfix
man:x:15:
dialout:x:18:
floppy:x:19:
games:x:20:
tape:x:33:
video:x:39:
ftp:x:50:
lock:x:54:
audio:x:63:
nobody:x:99:
users:x:100:
utmp:x:22:
utempter:x:35:
input:x:999:
systemd-journal:x:190:
systemd-network:x:192:
dbus:x:81:
polkitd:x:998:
colord:x:997:
printadmin:x:996:
libstoragemgmt:x:995:
rpc:x:32:
dip:x:40:
cgred:x:994:
ssh_keys:x:993:
saslauth:x:76:
abrt:x:173:
setroubleshoot:x:992:
rtkit:x:172:
radvd:x:75:
chrony:x:991:
unbound:x:990:
kvm:x:36:qemu
qemu:x:107:
tss:x:59:
libvirt:x:989:
usbmuxd:x:113:
geoclue:x:988:
gluster:x:987:
mysql:x:27:
pulse-access:x:986:
pulse-rt:x:985:
pulse:x:171:
gdm:x:42:
saned:x:984:
rpcuser:x:29:
nfsnobody:x:65534:
gnome-initial-setup:x:983:
sshd:x:74:
slocate:x:21:
avahi:x:70:
postdrop:x:90:
postfix:x:89:
ntp:x:38:
tcpdump:x:72:
stapusr:x:156:
stapsys:x:157:
stapdev:x:158:
vboxsf:x:982:
vboxdrmipc:x:981:
Fabio:x:1001:
marketing:x:1002:Fabio
networking:x:1003:host1
host1:x:1004:
legaldept:x:1005:
graphdept:x:1006:
simone:x:1007:

In this example simone, host1, Fabio are users, but they are shown anyways. It’s normal?
I was expecting only groups.
In this case I made them so I’m able to distinguish them. But is possible to show only actual grups?
Thank you in advance =)