Which of the following best describes a use case?

A use case is best described as an interaction between an actor and a system because it encapsulates the functional requirements of a system as seen through the user's perspective. In this context, an "actor" represents any entity that interacts with the system, which can be a user or another system. The use case outlines how the actor engages with the system to achieve a specific goal, detailing the steps involved in that interaction.

This approach helps to capture the essential functionality required from the system, making it easier to understand how the system is expected to behave in real-world scenarios. Use cases are widely utilized in requirement gathering and analysis because they provide a clear narrative that bridges communication between stakeholders, such as business analysts, developers, and users, ensuring that their needs and expectations regarding system behavior are well-understood and met.

The other choices do not accurately capture the essence of what a use case entails. A financial projection pertains to budgeting and forecasting, evaluating employee performance is focused on human resources and management practices, and a specification of system requirements, while related, is broader and encompasses more than just the interactions described in a use case.