Black-box testing is a software testing method that evaluates the functionality of an application without knowing its internal code structure. Testers focus on input and output, ensuring that the software behaves as expected based on requirements. This approach helps identify discrepancies between the actual and expected results. In black-box testing, various techniques such as equivalence partitioning and boundary value analysis are used to create test cases. This method is beneficial for validating user interfaces and overall system behavior, making it a crucial part of the software development lifecycle, especially in quality assurance processes.