There are basically three types of users in an organisation.
An admin of an organization is a user that has privileges that include modifying product access privileges for other members, inviting and removing members from an organization, and changing member roles. An Organization can have more than one admin. All admins are also a member of an organisation. An admin can view all the documents of an organisation
A billing admin of an organisation is a user that has privileges which includes access to the payment app. A billing admin has the rights to manage subscription and payment methods, and download receipts for the organisation. A member can also be a billing admin. It is not necessary for the billing Admin to also be an admin of the organisation. There can be only one billing admin in an organisation at a time.
A member of an organisation is a user who can use the products for which access privileges have been granted. A member doesn't have any special privileges. A member can not view the documents that their colleague is working on unless they are added to the document.