A role is a predefined set of privileges. Privileges define individual rights that a user requires to perform actions and read properties. Workstation Pro includes a default set of system roles. You can also create your own roles.
A single user might have different roles for different objects. For example, if you have two shared virtual machines, virtual machine A and virtual machine B, you might assign a particular user the Administrator role on virtual machine A and the Read Only permission on virtual machine B.