9c Individual Product Use Cases
Use cases are similar to scenarios, in that both tell the story of how the system interacts with the user(s) in response to some business event or while conducting some business task.
The difference is that use-cases are much more formal, with certain pre-determined sections for each use-case, and that use-cases indicate clearly what action the system takes in response to what actions taken by the user.
For example, here is Figure 4.7 from "Object Oriented Software Engineering" by Bruegge and DuToit: