FM, or Frequency Modulation is a method of audio synthesis, where by a carrier signal is modified by another signal which has been added to it, creating a completely new signal. The method works very well in recreating complex and percussive sounds that occur in the real world, with electronic equipment.
P.S. This is not a guide to Max or tutorial on synth building (that's what the built in lessons are for right?), I will not be explaining in depth just stating the development and changes I have made so that I can look back if I need to remember something or reference in my report.