What is the purpose function key when activate the second on a dual purpose key?

The purpose of the function key (often labeled as "Fn") when activating the second function on a dual-purpose key is to allow users to access alternative features or commands that are not available through the primary function of that key. For instance, on many laptops, the F1-F12 keys serve as either function keys or as shortcuts for hardware controls (like volume or brightness). By holding down the Fn key while pressing a dual-purpose key, users can toggle between these functionalities, enhancing overall efficiency and usability.