Mailbox Mailboxes are assigned a single role assignment policy. When a mailbox is assigned a role assignment policy, the assignments between management roles and a role assignment policy are applied to the mailbox. This grants the mailbox all of the permissions provided by the management roles.
Management role assignment policy The management role assignment policy is a special object in Exchange 2013. Users are associated with a role assignment policy when their mailboxes are created, or if you change the role assignment policy on a mailbox. This is also what you assign end-user management roles to. The combination of all the roles on a role assignment policy defines everything that the user can manage on his or her mailbox or distribution groups.
Management role assignment A management role assignment is the link between a management role and a role assignment policy. Assigning a management role to a role assignment policy grants the ability to use the cmdlets and parameters defined in the management role. When you create a role assignment between a role assignment policy and a management role, you can't specify any scope. The scope applied by the assignment is based on the management role and is either Self or MyGAL. For more information, see Understanding Management Role Assignments.
Management role A management role is a container for a grouping of management role entries. Roles are used to define the specific tasks that a user can do with his or her mailbox