The camera captures a grayscale video signal (baseband). This signal modulates the amplitude of a high-frequency carrier wave. Brighter parts = higher amplitude. This is Amplitude Modulation (AM).
The audio signal modulates the frequency of a separate carrier, offset +4.5 MHz from the video carrier. Louder audio = more frequency deviation. This is Frequency Modulation (FM).
Both modulated carriers are combined (superimposed) into a single RF signal and transmitted over a specific TV channel (e.g., Channel 2 = 55.25 MHz video carrier).
Your TV's tuner selects the desired channel, then separates video and audio carriers. The AM video is demodulated to recover the picture. The FM audio is demodulated to recover sound. Mistuning causes snow, rolling, and herringbone interference!