/etc/passwd

hplip:x:105:7:HPLIP system user,,,:/var/run/hplip:/bin/false
gdm:x:106:111:Gnome Display Manager:/var/lib/gdm:/bin/false
jeremy:x:1000:1000:Jeremy Anderson,,,:/home/jeremy:/bin/bash

Red is username, blue is numeric UserID (uid), lime is numeric GroupID (gid), green is user's full name which is sometimes called 'comment' or GECOS. Orange is for the user's home directory, and yellow is the user's shell program.

/etc/shadow

hplip:!:13377:0:99999:7:::
gdm:!:13377:0:99999:7:::
jeremy:$1$scn0C88t$242zylpPwvLRWhiqKpf8E0:13377:0:99999:7:::

Red is username, white is encrypted password, lime is when password was last changed (measured from 1/1/1970), tan is minimum password age, orange is maximum pasword age, gray is how much warning a user gets of an expiring password, then days after password expires that account is disabled, then an unused field.

/etc/group

scanner:x:110:cupsys,jeremy
gdm:x:111:
jeremy:x:1000:
admin:x:112:jeremy