A tribe is an interest community that shapes who you meet. Join one and future matches can be drawn from souls in the same tribes as you. It is a signal for matching, not a chat room.
Public tribes are open to join from Explore. Private tribes are joined by invitation or code and never appear in public discovery. Everyone belongs to the default EverConnected tribe automatically.
In your Soul Search preferences you choose which of your tribes join your match pool, with one mode across them all: Prefer, tribe souls first and then everyone, or Only, strictly tribe members. Your free plan includes one tribe in the pool; combining several is part of paid plans. Tribe pages and rosters show Soul IDs only, like everywhere else.