What constitutes a user story?
A user story is an informal, general explanation of a software feature written from the perspective of the end user or customer. The purpose of a user story is to articulate how a piece of work will deliver a particular value back to the customer.
What user stories are not?
User Stories do not specify the implementation details, and they are not passed on to the Developers. Instead, User Stories define context around the user, the need, and its importance, and then spark a conversation between the Product Owner and the Developers.