Role Membership

I was looking at my users and realized none of my users are members of
a specific group or role. Not sure if there's a difference between the
two (role / group) in PostgreSQL, is there?

easports=# \du
List of roles
Role name | Attributes | Member of
-----------+-----------------------------------+-----------
carlos | Superuser | {}
postgres | Superuser, Create role, Create DB | {}

Now my question is about the section 'Member of' and how this is
commonly utilized by most PG administrators. Is this the same thing as
explained here:

http://www.postgresql.org/docs/8.2/interactive/role-membership.html

If I am not mistaken I can simply create a role called 'accounting'
and add several users to the 'accounting' group rather than juggling
several dozen user grants, correct? If anyone can please tell me if
I'm hot or cold on this issue as well as anything you would think is
helpful for me to know that is not in the documentation that you
learned as a PG administrator.

Thanks so much!