What is the difference between admin roles in Office365

Role	What they do in Office 365
Global administrator	Accesses all administrative features in the Office 365 suite of services in your plan, including Skype for Business. By default the person who signs up to buy Office 365 becomes a global admin. Global admins are the only admins who can assign other admin roles. You can have more than one global admin in your organization. As a best practice we recommend that only a few people in your company have this role. It reduces the risk to your business. Tip: Make sure everyone who is a global admin in your organization has a mobile phone number and alternate email address in their contact info. Check out Change your organization's address, technical contact email, and other information for more details.
Billing administrator	Makes purchases, manages subscriptions, manages support tickets, and monitors service health.
Exchange administrator	Manages mailboxes and anti-spam policies for your business, using the Exchange admin center. To learn more, see About the Exchange Online admin role.
SharePoint administrator	Manages the document storage for your business on SharePoint Online. They do this in the SharePoint admin center. They can also assign other people to be Site Collection administrators and Term Store administrators. To learn more, see About the SharePoint Online admin role.
Password administrator	Resets passwords, manages service requests, and monitors service health. Password admins are limited to resetting passwords for users.
Skype for Business administrator	Configures Skype for Business for your organization and reviews usage reports. To learn more, see About the Skype for Business admin role.
Service administrator	Opens support requests with Microsoft, and views the service dashboard and message center. They have “view only” permissions except for opening support tickets and reading them. Tip: People who are assigned to the Exchange Online, SharePoint Online, and Skype for Business admin roles should also be assigned to the Service admin role. This way they can see important information in the Office 365 admin center, such as the health of the service, and change and release notifications.
User management administrator	Resets passwords, monitors service health, and manages user accounts, 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.
Microsoft Dynamics CRM Online	There is no Office 365 admin role specifically for Microsoft Dynamics CRM Online. Rather, when a person is assigned to the Office 365 global administrator role, they are automatically assigned to the System Administrator security role in CRM Online. A person assigned to the System Administrator security role in CRM can assign other people to CRM security roles. With the System Administrator security role, you can manage all aspects of CRM. For more information about CRM Online security roles, see this CRM article on Microsoft TechNet: Manage subscriptions, licenses, and user accounts.