Circles have a few different Roles.
VIP - This is the most important person in a Circle! This is your Mom, Dad, or other vulnerable family member.
Contributor - These are the people who help make your VIPs life a little bit better, contributing to your private Circle with content and love.
Guardian - These users are responsible for ensuring that your VIP has a good experience in the Circle, ensuring no harmful posts or comments are in the Circle, as-well as inviting new Contributors in.