Scenarios and use cases are essential tools in UX/UI design for understanding and planning how users interact with a product or application. A scenario is a narrative description that outlines how a typical user engages with the system in a particular situation, considering their goals, motivations, and potential obstacles. Use cases provide detailed descriptions of specific user-system interactions, often structured as step-by-step flows. Both approaches help designers capture user needs and expectations to create user-centered solutions. By developing scenarios and use cases, potential issues can be identified early, allowing for an optimized user experience.