AM and FM are forms of sound transmission in the form of radio waves. AM stands for Amplitude Modulation while FM stands for Frequency Modulation. Modulation is the manipulation of radio waves in order to transmit a meaningful (and translatable) signal. Morse code over electrical wires is modulation in that the series of dots and dashes are a standard code. AM and FM are different in how the radio wave is modulated. AM uses amplitude (or overall strength of signal) to transmit the message. FM uses frequency modulation (or manipulating the ‘spaces’ between the radio waves) to transmit the message.