Full form of FM is Frequency Modulation.

FM (Frequency Modulation) is also known as Frequency Modulated Electromagnetic Wave. FM is used for the broadcasting of Radio and several other applications of radio communication.

FM was invented in 1933 by American engineer Edwin Armstrong, wide band FM is used worldwide to provide high fidelity. FM is used for most of the broadcasts of music or general audio .

FM is a technique of transmitting information using a carrier wave.  The frequency of a carrier wave is carried according to the amplitude and polarity of the input signal. FM radio stations use very high frequency range of radio frequencies.

Full form of AM is Amplitude Modulation, also known as Amplitude Modulated Electromagnetic Wave.

FM and AM, both are used for broadcasting of radio but AM and FM both are different. AM is prone to interference because the amplitude of AM signals can be altered easily. On the other hand, FM is much less prone to interference because the amplitude of FM signals cannot be altered easily.

Comparatively the frequency range of FM radio is higher as it ranges from 1200 to 2400 bits per second or 88 to 108 MHz.