We here at NetNerds get a lot of questions on a daily basis, but we get a lot of inquiries regarding the function keys. The function ( or "F") keys on the top of your keyboard are shortcuts that are mostly used to re-enter previous commands without retyping them.
F1: Tapping or holding this key will retype the command that you just entered letter by letter.
F2: Copies the current command up to a specified character.
F3: Completely retypes the previous line that you entered.
F4: The reverse of F2 -- auto-deletes up to a specified character (your cursor must be in front of the text).
F5: Retypes the previous command like F3 but lets you cycle back through many lines in your command history.
F6: Inserts Ctrl+Z (^Z) in the Command Prompt, which is an end-of-file indication (text after this is ignored)
F7: Opens a list of previously entered commands that you can select from.
F8: Works like F5 but doesn't stop at the end of your command history, cycles back to the start.
F9: Lets you retype a previous command by entering a number associated with the line.