A User story describes a desired feature (functional requirement) in narrative form. It is usually contains a name, description, screen and external documents, and information about how the implementation will be tested and adheres to the INVEST acronym. User stories are usually written by the product owner, and are their responsibility. As a Backlog Item it fulfills the following template:
It may need to fulfill more criteria to qualify for Readiness.
A User Story goes through a process called "the 3 Cs". These are:
Card (template above)
Conversation (discussion of what the template requires)
Confirmation (acceptance criteria for the user story)