A test plan in software testing is a key document that provides a structured approach to validating a software application. It details the testing objectives, scope, resources, tools, and timelines, ensuring that all aspects of the software are examined. The plan includes test cases, responsibilities, risk analysis, and criteria for starting and completing the tests. This organized framework helps teams execute the testing process efficiently, uncovering defects and ensuring quality assurance. A well-prepared test plan is essential for delivering software that meets user expectations and performs reliably in real-world scenarios.