Product backlog is an ordered and emerging list of everything that may be needed for the Product. Product backlog is one of the three artifacts of the Scrum frame-work. Product backlog items have Description, Order, Estimate, Value.
It is an ordered List of Items which may include features, functions, requirements, enhancements and fixes. It is a single source of requirements and is an emerging list. The Product Backlog is owned by the Product Owner and is prioritized by the Product Owner. Only the Product Owner can change priority. Anyone can add to the list. It is progressively elaborated, never complete and is managed through ongoing backlog refinement.
The Product Owner is responsible for its content, availability and ordering. The Product Owner provides clarification on the product backlog if the team has any questions.
The Development Team provides estimates and creates the Product Increment.
The ScrumMaster finds techniques for effective Product Backlog management and helps understand the need for clear, concise Product Backlog Items
The items in the top are usually clearer, have more detail and usually generate high value when a shippable product is created based on this order. Mike Cohn emphasizes the importance of a well refined product backlog and uses DEEP (detailed appropriately, Estimated, Emergent, Prioritized) to summarize key attributes of a good product backlog.
The Product Backlog is DEEP:
I was on a trip with my family where we were on a boat, I saw various water creatures coming up from the bottom. Creatures were of varying sizes, colors, shapes and looked either clear or not so clear about where I was looking at them from. I relate this to the product backlog that has different features, functions, requirements, varying level from detail and their sizes and where they are located in order.
I recommend my teams to have a backlog that is detailed enough, enough so they can ask the right questions, they can estimate and select these items in Sprint Planning so they can create a product increment. The product backlog needs to be ready just in time, just in time so Sprint Planning goes smoothly. I recommend at least 2 to 3 Sprints worth of product backlog items so we reduce or eliminate waste. It is not recommended to refining the entire backlog because of this reason.