A Functional Requirements Document (FRD) is a formal document that outlines the specific functionalities and features that a system or product must have. It serves as a guide for developers and stakeholders, detailing what the system should do to meet user needs. The FRD typically includes use cases, user stories, and acceptance criteria to ensure clarity and alignment among all parties involved. The purpose of an FRD is to provide a clear understanding of the project requirements before development begins. This helps prevent misunderstandings and scope creep, ensuring that the final product meets the expectations of users and stakeholders, such as project managers and clients.