A user story is a concise, plain-language description of a product or capability written from the perspective of the user. A user story, according to many agile professionals, is the smallest unit of product development effort that may lead to a full piece of user functionality. Product teams choose to break development work into user stories rather than product features or product requirements for a variety of reasons, including ease of understanding, representing but small enough deliverables to fit in sprints, assisting teams in focusing on real people, and building momentum by providing development teams with a sense of progress.