A user story is an agile version of a project requirement. A user story is comprised of a couple of sentences that defines who, what and why for a given requirement. User stories are written by the business user to communicate the software need or want.
It depicts the following information.
As a
<user>
I want to
<What is the Purpose>
So that
<What you gain by this story>
eg.
As a
Customer
I want to
Login to the IRCTC website
So that
I can book journey tickets
