A PhotoCircle Essentials seat is required for those who work for, or on behalf of, your company/organization and use PhotoCircle.

Needs a Seat (Paid)Doesn't Need a Seat (Free)
EmployeesCustomers
StaffVolunteers
FacultyParents
ContractorsThe Congregation

For example, an organization may have 1000 employees but only 5 of those employees use PhotoCircle. In this case, they would require 5 seats.