What does FM and AM mean? How did the radio receive music?

If you want to send a signal out, the signal must be a high-frequency signal. The low-frequency signal cannot be transmitted too far. Our voice and image are always a low-frequency signal. We must first turn it into a high-frequency signal. This process is called Modulation .We change it into a high-frequency signal. The amplitude of this signal changes with the change of the low-frequency signal. This kind of signal is called the AM signal or AM.
If I let the frequency of the high-frequency signal change with the change of the low-frequency signal, this is called FM signal. That's FM.
There are three kinds of wave propagation modes in the signal propagation mode. In addition, the basic principles of demodulation are also explained in the video. Please gradually realize that the above principles are also common for mobile phones.