What Is a Use Case?

A simple description of what a user expects from a system in a particular interaction — representing a discrete task that involves external interaction with the system

Explanation

A use case can be taken as a simple description of what a user expects from a system in that interaction. Each use case represents a discrete task that involves external interaction with the system. In its simplest form, a use case is shown as an ellipse with the actors involved shown as stick figures.