Scenarios are descriptions of one or more users interacting with with a system, device, or process to achieve a goal under specified conditions and constraints. They provide information about the context in which a system has to operate, in a user- and task-oriented way.
Scenarios can be presented as rich narratives (e.g.,an hour or a day in the life of a user) or simple statements describing the triggers and situation that prompts a user to interact with a system. Scenarios sometimes include simple lists of the steps in a task. Scenarios are used in design sessions, walkthroughs, and usability tests to ensure that the system design effectively supports users in a wide range of real-life situations.
They are also known as "task scenarios".
Scenarios and use cases
Scenarios are sometimes called "use cases". However the term "use case" can be confusing, as it is used with a different meaning in software engineering. One way of illustrating the difference is through the classic example of withdrawing money from a bank.
User-centered design usually tries to have a scenario refer to multiple component use cases (depending on functions required to satisfy the goal of the scenario), and also to have a use case refer to multiple scenarios (depending on the likely triggering situations and goals that reflect the overall expectations for the system in user terms).