Scenarios are paradoxically concrete but, rough, tangible but flexible, they implicitly encourage “what-if?” thinking among all parties. They permit the articulation of design possibilities without undermining innovation. Scenarios compel attention to the use that will be made of the design product. They can describe situations at many levels of detail, for many different purposes, helping to coordinate various aspects of the design project.

(Carrol. Making Use: Scenario-based Design of Human-Computer Interaction)