Functional requirements are specific statements that describe what a system, product, or service must do to meet user needs. They outline the expected behavior, features, and functions that the system should provide. For example, a software application might require a user to be able to log in, search for items, and make purchases. These requirements serve as a guide for developers and stakeholders during the design and implementation phases. They help ensure that the final product aligns with user expectations and business goals. Clear functional requirements can also facilitate testing and validation, ensuring that the system performs as intended.