The Product Backlog is a prioritized list of everything that might be included in a product. The Product Owner creates, maintains, and regularly re-orders the Product Backlog. The Product Owner uses the Product Backlog to adapt to emerging requirements, customer feedback, and market changes.
The Product Backlog is the manifestation of the vision and the business case for the product. The backlog is made up of Product Backlog Items (PBIs). PBIs can be anything from market requirements, to use cases, to specifications. However, the best practice is User Stories. Whatever the team decides on, it is critical to represent the end user’s perspective.
PBI’s at the top of the Product Backlog should be refined and immediately actionable. Items further down the backlog need less definition and can reflect bigger ideas. These larger chunks will need to be broken down into smaller pieces as they approach the top of the Product Backlog.