What are the main differences between a use case and a user story?
A use case describes a business process or a self-contained task within a process. It is as complete as possible, lasts as a document, is agreed (by customers and developers) and is used to generate requirements.
A user story is small enough to be implemented in a single iteration, represents an instance from a user perspective, is not complete, does not last and instead is used as a reminder for a conversation.