What is the distinction between functional and non-functional requirements?

What is the distinction between functional and non-functional requirements?

Ans: Functional requirements: These are the statements of the services the system should provide, how the system is going to react to particular inputs and how the system should behave in particular situations.

Non-functional requirements: These are constraints on the services or functions offerred by the system, which include timing constraints, constraints on the development process and standards. These often apply to the system as a whole.