What are the key differences between AM and FM modulation?

In AM (Amplitude Modulation), the carrier amplitude varies with the message signal while frequency remains constant. In FM (Frequency Modulation), the carrier frequency varies while amplitude stays constant. AM is simpler and requires less bandwidth but is susceptible to noise and interference. FM provides better noise immunity (amplitude variations can be limited), better audio quality, but requires wider bandwidth. AM is used in long-wave broadcasting; FM is used for high-fidelity audio and mobile communications.