A story, also known as a user story or a product backlog item in Scrum, is the unit of business value from which task level work is derived. Stories are always prioritized in rank order relative to other stories in the product backlog. The story essentially represents a promise that work will be performed by the team and that a conversation will occur in order to iron out the exact details of the story when selected for implementation. Every story should provide value to the end user and should be sized appropriately, with the intent to be completed within a single time-boxed iteration.

Agile best practices state that each story should contain an estimate provided by the team, and should remain transparent and completely testable throughout its lifecycle. Stories may be related, but every effort should be taken to define a single story technically independent of other stories. At the conclusion of each iteration, stories are reviewed and accepted (or rejected) by the product owner, and new stories are prioritized to be part of the next iteration.