FM radio, or Frequency Modulation radio, is a type of radio broadcasting that uses a frequency modulation technique to transmit sound. In analog FM radio, the amplitude of the carrier signal is constant, while the frequency of the carrier signal varies in accordance with the audio signal. This is in contrast to AM radio, or Amplitude Modulation radio, which uses an amplitude modulation technique to transmit sound, where the amplitude of the carrier signal varies in accordance with the audio signal.
Analog FM radio is still widely used around the world, although digital radio is becoming increasingly popular. Digital radio uses digital modulation techniques to transmit sound, which results in a higher quality sound and is more resistant to interference than analog FM radio.