The group is a beta test group providing early-stage feedback on some, but not all, new Wikia features. Because it is possible that some of these features may never move from development to production, access to the Council wiki is restricted. However, not all features that are have been beta tested by the Council.
In short: Not all features beta tested by the group are rolled out; and, not all features rolled out have been beta tested by the group.
The group is selected from the entire Wikia community, sitewide. Membership is rotated every few of months to allow fresh feedback from different users. The group is managed by the Community Council Project Manager, Sarah Manley.
A list of members can be found at Special:ListUsers/council.