Final answer:
To use a numbered function key on a laptop computer, you often need to press the 'Fn' key simultaneously with the function key you wish to activate.
Step-by-step explanation:
When using a laptop computer, you must sometimes press the Fn (Function) key in order to use a numbered function key (F1, F2, etc.). These function keys often have two modes of operation: one is activated by pressing the key on its own, and the other requires you to hold the Fn key simultaneously. The alternate function is typically indicated by a symbol or text on the key that's often in a different color, denoting the need to press the Fn key to access that function. This is common for laptop keyboards where space is limited, and the keys must serve multiple purposes.