Product owner
Product owner owns the product backlog which include creation, elaboration, prioritization, validation and value maximization. In other words, product owners primary role is product backlog grooming and value delivery. The product owner is considered as one who understands the functionality better than everybody else in the team. Here are the key roles and responsibilities of the product owner;
Accountable for maximizing the value of the product
Developing and explicitly communicating the product goal
Creating and clearly communicating the product backlog items
Prioritizing the product backlog items
Maintaining the clarity, transparency and the visibility of the product backlog