group(5) -- Linux man page
NAMEgroup - user group file
DESCRIPTION/etc/group is an ASCII file which defines the groups to which users belong. There is one entry per line, and each line has the format:
The field descriptions are:
- the name of the group.
- the (encrypted) group password. If this field is empty, no password is needed.
- the numerical group ID.
- all the group member's user names, separated by commas.
SEE ALSOlogin(1), newgrp(1), passwd(5)