Functional requirements are specific statements that describe what a system, product, or service must do to meet the needs of its users. They outline the expected behavior, features, and functionalities that the system should provide. For example, a mobile application might have functional requirements such as user authentication, data storage, and the ability to send notifications. These requirements serve as a guide for developers and stakeholders during the design and implementation phases. By clearly defining what the system should accomplish, functional requirements help ensure that the final product meets user expectations and performs its intended tasks effectively.