whats the huge difference between "f" and "ff" in classical music?

Answer 1

Both of the other responders were correct. But you'll want to also note that forte and fortissimo aren't limited to classical music. You will also find these in movie sound track scores and other music genres where there is character (different volume levels) in the music. Today's rock sounds like it is all ff to me.

Answer 2

f = forte which means loud
ff = fortissimo which means very loud.

you need to look at the piece of music that you are playing and put the f and ff into perspective of the piece.

Answer 3

'f' is loud (forte), and 'ff' is very loud (fortissimo)