I’m a visual person so having something I can see and experience typically helps me understand someone’s idea better than if they’re describing something and I’m trying to imagine it. It also helps to have a concrete artifact because we can methodically catalogue its characteristics and define which ones are exactly what the person means, kind of what they mean but they still need help refining it, or completely up for grabs. This is why I find prototypes, wireframes, and sketches to be useful tools for defining the solution space.