What best describes a 'use case'?

A use case is fundamentally a description of how users interact with a system to achieve specific goals. It outlines the sequence of actions taken by users and the responses of the system, which helps in understanding the functional requirements of the software or application being developed. By detailing these interactions, use cases facilitate clear communication among stakeholders about how the system should behave in various situations.

This representation is vital for business analysts as it aids in identifying and documenting requirements, ensuring that the developed system meets user needs effectively. Use cases typically include various components, such as actors (users or other systems that interact with the system), preconditions, postconditions, and the main flow of events.

The other options do not accurately capture the essence of a use case. Scenarios for evaluating financial impact, stakeholder feedback, and project proposals do not pertain to the specific functional interactions users have with a system, which is the core focus of a use case.