There may be sub-sections in your organisation where it is more appropriate for the people involved to have a separate address book. This is catered for by making an Independent Group. Independent groups have a different icon to normal user groups –
Independent groups are a special type of group folder with a separately maintained database of people. They are often used for activities which involve people from outside your organisation such as the 'parents and toddlers' group. You can delegate people to maintain the contact information for an independent group without having access to the full main contact database.
Independent groups also allow you to provide restricted access to your web site; part of the registration process requires new applicants to indicate which areas of the web site they would like to register with. A member who is registered only with the "football team" independent group may not see articles, events and forums restricted to members of the organisation, and would only see contact details for other members of the "football" group in the address book area.
You can make a group independent by checking the independent option within the Group Properties accessed via the Group Settings icon on the top right.