Integration testing and functional testing are two critical components of software testing, each serving distinct purposes in ensuring software quality. Integration testing focuses on the interaction between software modules, verifying that they work together seamlessly without errors, and typically follows unit testing. It employs grey-box testing techniques and is suited for detecting issues that arise when modules are combined, though it can be complex and resource-intensive. Functional testing, on the other hand, is a black-box technique that evaluates whether software functions as intended in real-world scenarios, ensuring it meets user requirements and performs correctly. It generally follows integration testing and can coincide with system testing. While integration testing addresses component interactions, functional testing focuses on verifying specific software functions and features, aiming to detect deviations from expected behavior. Both testing types are essential for robust quality assurance, offering complementary insights that help software teams deliver reliable and user-friendly applications.