A tribe is a group of humans who live and work together, often times possessing their own unique culture and beliefs.
Following an unknown turn of events, the human population was severely decimated and reduced in number. This resulted in the loss of their technological advancement and knowledge, as well as the regression of their civilization. In order to adapt to the natural world once again, human societies were reshaped into small groups of people, hoping to survive in a world ruled by the now dominant machines.
These groups or tribes adopted a way of life similar to their ancestors, hunting and gathering for food and materials. Eventually, tribes grew larger, some even turning their villages into towns and small cities, and developed an economy based on resources obtained from machines.