A user story is a brief description of a feature of the system. Stories are small, taking only a week or two to
develop. The best stories provide direct business value. When stories are too big, they must be split. Consequently, it
may take multiple stories to provide business value. In this case, the individual stories need to demonstrate to the
customer that the team is making progress toward the desired business value.
There is no need for a lot of detail in the description. The details will be flushed out when the acceptance tests for
this story are defined. Typically, XP user stories are written on small index cards, one story per card.