Scrum : Different Product owner and Project Manager

I have created a short document of two authors : Ken Swchaber and Jeff Sutherland. At definition in this document about Product Owner:

The Product Owner is the sole person responsible for managing the Product Backlog

I see that Product owner is very like to Project Manager in normal software development process.

So, what does a real difference, or just the same.

The Product Owner and a Project Manager are quite different.

On a traditional project, a Project Manager, as the title implies, manages a project.

However, on a Scrum project, the Development Team manages their own work.

The Product Owner, while responsible for maximizing the value of the product and the work of the Development Team, is the sole person responsible for managing the Product Backlog.

Product Backlog Management includes:

• Clearly expressing Product Backlog items;
• Ordering the items in the Product Backlog to best achieve goals and missions;
• Ensuring the value of the work the Development Team performs;
• Ensuring that the Product Backlog is visible, transparent, and clear to all, and shows what the Scrum Team will work on next;
• Ensuring the Development Team understands items in the Product Backlog to the level needed.

Hope that helps. More details available in this article on the need for Product Owners