Stories are units of customer visible functionality. A story has an estimate – a measure of the development effort required to implement it.
Giving a story an estimate gives the business feedback on how difficult a feature is to implement. The story can be discussed and its scope can be expanded or split.
A story has a short title and a brief description of what is involved in delivering the feature. A story is usually written on an index card and placed on a story wall. Some teams prefer to use electronic systems like Jira and Trello
The name ‘story’ is used to differentiate this from traditional software engineering (waterfall) requirements that are seen as mandatory. XP teams usually write stories on index cards. They can be easily re-written if they need to be revised or turn up if they are no longer required.