How is a use case best described?

A use case is best described as an observable interaction between actors and a solution because it focuses on how users (the actors) interact with the system to achieve a specific goal. Each use case outlines a scenario in which an actor engages with the system, detailing the steps involved and the expected outcomes. This approach emphasizes the functionality and behavior of the system from the user's perspective, highlighting the various ways in which users will interact with the application or process to accomplish their objectives. By capturing these interactions, use cases provide valuable insights for both developers and stakeholders, ensuring that the system is designed to meet the users' needs effectively.