UseCases

Use cases: In software engineering, a use case is a technique for capturing functional requirements of systems and systems-of-systems. Each use case provides one or more scenarios that convey how the system should interact with the users called actors to achieve a specific business goal or function. Use case actors may be end users or other systems. Use cases typically avoid technical jargon, preferring instead the language of the end user or domain expert. Use cases are often co-authored by business analysts and end users.
(Source: Wikipedia)