Business requirements usually consist of both functional requirements and non-functional requirements. The plan for implementing functional requirements is detailed in the system design. The plan for implementing non-functional requirements is detailed in the system architecture.
functional requirement defines a function of a software system or its component.
A function is described as a set of inputs, the behavior, and outputs. may be calculations, technical details, data manipulation and processing and other specific functionality that define what a system is supposed to accomplish. Behavioral requirements describing all the cases where the system uses the functional requirements are captured in use cases
non-functional requirement is a requirement that specifies criteria that can be used to judge the operation of a system. Like security , usability,testability, maintainability, extensibility and scalability
Business requirements are often listed in a Business Requirements Document or BRD. The emphasis in a BRD is on what is required, rather than on how to achieve it, which is usually delegated to a Systems Requirements Specification or Document (SRS or SRD) or other variation such as a Functional Specification Document. While supposedly describing the product, system, or software from an external perspective, such documents often define the product/system/software requirements in the context of a chosen technology (a solution approach or architecture).