A use case is a simple, structured story of how a user interacts with a system to achieve a specific goal, written from the user’s point of view. It focuses on the steps between an actor (user or external system) and the system that lead to an outcome that has clear value, like “place an order” or “reset a password.”

Basic idea

  • A use case describes a sequence of actions between a user and a system that produces a meaningful result, such as completing a purchase or submitting a form.
  • It is usually written in plain language so that business stakeholders, developers, and testers can all understand it easily.

Key elements

Most use cases include:

  • Actor : The person or external system interacting with the software (for example, “Customer” or “Payment Gateway”).
  • Goal : The outcome the actor wants, such as “Update profile” or “Request refund.”
  • Main flow : The normal, successful path of steps from start to finish.
  • Alternative / exception flows : What happens if things go differently (wrong password, payment declined, missing data, and so on).
  • Preconditions : What must already be true before the use case can start (for example, “User is logged in”).
  • Postconditions : What is true after it completes successfully (for example, “Order is stored and confirmation email sent”).

Why use cases matter today

  • They help capture and clarify functional requirements by focusing on what users actually need the system to do, instead of only technical details.
  • Teams use them to guide system design, testing scenarios, and even user documentation, because each use case naturally suggests test cases and help topics.
  • In modern projects (including agile), use cases often complement user stories by adding more detailed step-by-step behavior when needed for complex flows.

Simple example

Imagine an online portal where a customer updates personal information:

  • Actor: Customer.
  • Goal: Complete or update the customer profile.
  • Main flow (simplified): Customer logs in, system verifies identity, system shows profile form, customer updates data, system saves and confirms the changes.

This small narrative is a “use case” because it shows one coherent way a user interacts with the system to achieve a valuable result.

TL;DR: A use case is a user-focused, step-by-step description of how someone interacts with a system to achieve a specific, useful goal, and it is used to capture and communicate functional requirements.