Introduction
In Terraform Cloud, Business tier customers are only charged for "admin" users who are managing the Application/Organization(s), and there is no cost associated with any "standard" user seats. In essence, this is the difference between Managers of the platform and Consumers of the platform, with only the former considered as "users" from a licensing perspective.
Outcome
The "Active admin users" metric displayed in the "Usage" tab in Terraform Cloud is currently reflective of all users members of the "owners" team of a given Organization, as well as any users which have at least one of the following organization-level permissions listed here below:
Organization Access