A test case is a set of conditions or variables used to determine if a software application or system behaves as expected. It typically includes inputs, execution steps, and the expected outcome. Test cases help ensure that the software meets its requirements and functions correctly before it is released to users. In software development, creating effective test cases is crucial for identifying bugs and improving quality. They can be automated or executed manually, and they often cover various scenarios, including edge cases. Properly designed test cases contribute to a more reliable product and enhance user satisfaction with the final software application.