Explanation:

Functional requirements are features that are built to serve the products' users. They are pieces of functionality that solve particular problems for users. An example of a functional requirement would be: “User should be able to import contacts into their mail application.”
Function pertains to the outcomes or results produced based on the organization's function, or role, in its environment. It is what an organization does to fulfill its purpose. Function is the complement of structure -- entailing the notion of effect, the change in the environment due to the function, as in cause and effect. Function is the ends, the sake for which the function is performed, as in means and ends. Function encompasses the notion of output, both as something supplied by the system and as a place where offerings and information leave the system. See structure aspect and process aspect.