Both OnPremise Exchange server and Office 365 Exchange admin Center use a large set of predefined permissions, which can be used to grant permissions to your administrators and users instantly. Here the permissions features are used to set up role-based permissions for your Exchange server new organization up and running quickly.
In Exchange Server, the permissions that you grant to administrators and users are based on management roles. A role defines the set of tasks that an administrator or user can perform. When a role is assigned to an administrator or user, that person is granted the permissions provided by the role. Roles give permissions to perform tasks to administrators and users by making cmdlets available to those who are assigned the roles.
Now Office 365 admin center becomes Microsoft 365 admin center, and is tightly integrated with Azure AD, the role & role assignments are classified into two categories and are grouped under two names Azure AD and Exchange separately in the Roles → Role assignment section.
In the conventional Exchange admin center, now you can see two separate entities Classic Exchange admin center & Microsoft 365 admin center.On Roles, you have two sub-entities called Role assignments & Administrative units.
Read this blog, to know more about Administrative roles and End-user roles.
