One nice feature of AIX are commands
such as lsgroup that make it very easy to see all the members of a
group. On Linux, this is a little more difficult.
At first glance it might appear that
you can just look at the /etc/group file, find the group in question,
and see all of the users who are a member of the group from there.
However, the /etc/passwd file is what records each users primary
group membership, so if you only look in /etc/group you will miss
everyone who has a primary group set to the group in question.