From the wikipedia:

The Rainbow Family of Living Light, sometimes known as the "Rainbow Tribe", is an international loose affiliation of individuals who have a common goal of trying to achieve peace and love on Earth. Those who participate in, or sympathize with, the activities of this group sometimes refer to their group simply as the "Family". The words: Rainbow Family in the longer title are a reference to the group's inclusiveness of all colors or races. The use of the phrase: Living Light in the longer title is a reference to "living lightly", or living with little mass or impact on the environment. Rainbow family participants make the claim that their group is the "largest non-organization of non-members in the world". In addition to referring to itself as a non-organization, the group's "non-members" also even playfully call the group a "disorganization". There are no official leaders, no structure, no official spokespersons, and no membership. Instead, the Rainbow Family forms community through shared "traditions" of love for the Earth, and gatherings to pray for peace. It is maintained by councils consisting of any "non-member" who wishes to be part of the council.