[Zope] Concepts

[mixo]

Is there a way to  define a group in Zope?
For instance, could I have user1, user2 and user3 as
part of a group, say "testers", and the group "testers"
can access to certain folders (or something of that sort)
in  Zope.  I want  users within a group to be able do
updates on  folders that  group they belong to  has been
assigned to.

Mixo Shiburi
I have had a look at  "roles", and what they seem to do is
define permissions and not groups of people.