A typical usage of a system by an end user to accomplish his/her job is termed as a “Flow” or “Business Flow” or “End-to-end flow”. And this is accomplished by performing a collection of use-cases (or Requirements). And in the process the end user invokes the various features offered by the system.
So let us understand the connection between these three terms:
Flow = A set of requirements/use-cases done to accomplish a job
Requirement = An use case, typically involved invoking a set of features.
What an EUT is depends on the level – Click here to read about this.