The traditional project approach has three core roles - the Customer, the Project Manager, and the Project Team. Similarly, Scrum has three roles - the Product Owner (PO), the Development Team, and the ScrumMaster.

It’s easy to see that the Customer and the Product Owner map rather nicely, since both have the money and the business need. Also the Project Team and the Development Team map nicely, since they are the people who have the skills to create the product needed by the business. 

The last one is a bit trickier. It’s easy to think that they map nicely, too. But they really map only in the goal of that role - both roles want the project to succeed. But other than that, they are the two opposite sides of the “project leadership coin”.