how does the signal from a radio work?

Answer 1

That's a really general question.

Please start here...
http://electronics.howstuffworks.com/radio.htm

Answer 2

am WORKS by increasing the size of the signal and then decreasing it at the frequency of the audio signal that is being transmitted. The radio frequency is removed and all that is left is the sound or audio, that is amplified and it's the music you hear.

FM works by sending a radio frequency and increasing and decreasing the frequency at the same rate as the audio. This is a better method since you don't have to worry about noise spikes in the signal, since you're only worried about the frequency. You remove the carrier frequency and change the higher and lower freq to an audio signal and that is the music you hear.