
Explanation/Reference:
* User management admin: Resets passwords, monitors service health, and manages user accounts, user groups, and service requests. The user management admin can't delete a global admin, create other admin roles, or reset passwords for billing, global, and service admins.
* Global admin: Has access to all administrative features. Global admins are the only admins who can assign other admin roles. You can have more than one global admin in your organization. The person who signs up to purchase Office 365 becomes a global admin.
* Billing admin: Makes purchases, manages subscriptions, manages support tickets, and monitors service health.
Reference: Assigning admin roles
https://support.office.com/en-SG/article/Assigning-admin-roles-eac4d046-1afd-4f1a-85fc-8219c79e1504