Some employees carry out certain roles as part of their job. These roles are not tied to their position or salary. Employees may switch roles, for instance when joining a different team.
The Product Owner [Stylight login required] is the empowered central point of product leadership. She is the voice of the customer, has to understand the needs and priorities of the organizational stakeholders and has to communicate to the development team what must be built and the order in which to build it.
The Agile Coach [Stylight login required] focuses on helping everyone understand and embrace agile values, principles and practices. She acts as a coach to both the development team and the product owner.