The Product Backlog is an ordered list of everything that is known to be needed in the product. It is the single source of truth for the Scrum Team and the stakeholders. It contains all the requirements, features, functions, enhancements, fixes, and anything else that can deliver value to the customers and users of the product.

All types of requirements are acceptable on a Product Backlog, as long as they are aligned with the product vision and goals, and they are transparent, clear, and valuable. The Product Backlog can include stability requirements, performance requirements, product functionality, documentation, fixes, or any other aspects that contribute to the quality and usability of the product.

The Product Owner is accountable for maximizing the value of the product resulting from the work of the Scrum Team. The Product Owner is responsible for managing and refining the Product Backlog, collaborating with the stakeholders and the Developers, and ordering the items in a way that best achieves goals and missions. The Product Owner represents the interests of everyone with a stake in the product and ensures that the Scrum Team works on the right things at the right time.

The Developers are accountable for creating a “Done” Increment that meets the Definition of Done each Sprint. The Developers are responsible for planning and executing the Sprint Backlog, designing and building the product functionality, testing and improving the product quality, and delivering a potentially releasable Increment. The Developers work closely with the Product Owner to understand and clarify the Product Backlog items, provide feedback and estimates, and suggest improvements and innovations.

References:

Scrum Guide: https://www.scrumguides.org/scrum-guide.html

Product Backlog: https://www.scrum.org/resources/what-is-a-product-backlog