A tribe is one location, branch or business unit inside your organisation. Most organisations rename it — Stores, Offices, Centres — but tribe is the word the product uses.
A member belongs to one tribe
Or to none. A member with no tribe is an organisation-level member, and the list filters call these Organisation Members. Which you choose matters, because the tribe decides which payment gateway collects the money and which tribe the revenue is reported against.
Each tribe collects into its own account
Reporting by tribe
Recurring Revenue has a By Tribe table and the Sales Report has a Tribe Results tab, so you can see which locations carry the recurring revenue. Members with no tribe are reported separately rather than being spread across the others.
Settings are organisation-wide
Billing details, tax information, statement messages and reminder thresholds are set once for the whole organisation. There is no per-tribe settings screen.