Groups fulfill a whole range of functions.
It's probably fairly clear that some groups exist primarily to achieve aims beyond the satisfaction of their members. The group of members of an environmental pressure group are attempting to stop pollution, encourage the development of sensible environmental policies and so on. Other groups may be much more oriented towards the satisfaction of the group members' needs. The members of a French evening class, for example, are there for each of the individual members to learn French. Groups may also have unstated functions, far less obvious than the two we have mentioned.