What is a use case, what is a user story, and how do they differ?

Use case — is a formal description of the interaction between a user (actor) and the system to achieve a specific goal. It includes scenarios, start and end conditions, alternative paths, and exceptions. Use case helps understand how the system should behave in different situations.

User story — is a brief, informal description of functionality from the user's perspective, usually in the format: "As [role], I want [goal], so that [reason]." User story focuses on value for the user and is often used in Agile for task planning.

Differences:

• Use case is more detailed and formal, describing a sequence of steps and possible developments.
• User story is simpler and shorter, focused on business value and team communication.

Example of a user story:

As a user, I want to reset my password so that I can access my account if I forget it.

Example of a use case (part):

1. The user selects "Forgot password?"
2. The system requests email
3. The user enters email
4. The system sends an email with a link to reset the password
5. The user clicks the link and enters a new password
6. The system confirms the password change

Thus, the use case describes detailed steps, and the user story describes the user's goal and motivation.