A requirements traceability matrix associates business and functional requirements with use cases and test scripts that validate them. Relationships can be one-to-one, one-to-many, or many-to-one. Unique identifiers are needed for each requirement, use case, and test script. The matrix ensures complete testing and provides a basis for test planning. It can be a standalone document or part of other documents. Traceability prevents scope creep and ensures all requirements are satisfied.