A user story clearly and shortly describe what a typical user wants to achieve
and what kind of expectation she has from the product.
The user story identifies who the user is, what she needs, and why she needs it.
A use case is the list of steps a user might take in trying to get something done.
The wireframe helps to communicate abstract concepts with users to generate feedback.
Get users involved early in the design process.
Cover usability issues and validate conceptual decisions based on user reactions.