What is the Ambassador role? How does the earning team work?

As an Ambassador, you earn up to a 25% bonus on your base mining rate for each person you invite to the network.

You become an Ambassador when new members join your earning team by using your invitation code when they sign up for Pi Network. Each member of your earning team provides a 25% boost to your earnings when they are actively mining. A new member can only be added to their inviter’s earning team, because each member only joins Pi once using one inviter’s invitation code. In other words, unlike the security circles where people can be added into multiple member’ circles based on trust, earning teams are fixed based on who invited whom. Each invitee in the world can only be claimed by one inviter.