User stories are a simple, concise method for defining pieces of functionality from the user's perspective. 

A user story is often expressed in a simple template:

As a [type of user], I want [some goal] so that [some reason].

This format helps keep the focus on the user’s needs rather than the technical details of how the feature will be implemented.

Beyond the basic structure, user stories may also include:

• Acceptance Criteria: Specific, agreed-upon conditions under which a user story is considered complete and functions as intended. This is crucial for testing and validation.
• Attachments: Diagrams, mockups, or other visuals to clarify the requirements or expected outcomes.
• Comments/Notes: Any additional information that can help the development team understand the context or details of the user story.

Flow of a User Story is described : @Marina