A use case defines the interactions between a user (or "actor") and the system to achieve a specific goal. This service includes identifying and developing comprehensive use cases for different user roles and actions within the system. Each use case describes the sequence of steps the user takes, along with system responses, exceptions, and alternate paths. This documentation helps developers and testers understand exactly how the system is supposed to function in different scenarios, reducing ambiguities in requirements and ensuring the solution addresses real user needs.