A user story is a short, informal description of a desired feature written from the end user's perspective, following the format: "As a [type of user], I want [goal] so that [benefit]." For example, "As a customer, I want to save my shopping cart so that I can complete my purchase later." User stories are intentionally brief to encourage conversation between the team and the Product Owner about the details. Acceptance criteria define when the story is complete. The INVEST acronym describes good user stories: Independent, Negotiable, Valuable, Estimable, Small, and Testable.