Tribes is a new addition in the internet slang and express a mass gathering of people around a person, an idea, a technology, or a concept.
viewed, developmentally or historically, as a social group existing before the development of nation states, or outside them. A tribe is a group of distinct people, dependent on their land for their livelihood, who are largely self-sufficient, and not integrated into the national society. It is perhaps the term most readily understood and used by the general public to describe such communities. (Wikipedia: Tribe)
But in marketing, tribes have a slightly different meaning!
A Video About Tribes
Tribes is a concept that may empower ordinary people, in more that one ways.