The Scrum Product Owner has the vision of what to build and conveys that to the team. He or she focuses on business and market requirements, prioritizing the work that needs to be done, managing the backlog, providing guidance on which features to ship next, and interacting with the team and other stakeholders to make sure everyone understands the items on the product backlog.
Software Testers are responsible for the quality of software development and deployment. They are involved in performing automated and manual tests to ensure the software created by developers is fit for purpose. Some of the duties include analysis of software, and systems, mitigate risk and prevent software issues.