We listen to music on the FM car radio, or to a commentary on an AM pocket radio and we watch pictures sent by radio waves to our TV sets.
Industry uses it to dispatch vehicles, to send messages or to monitor processes.
Law Enforcement and Public Safety would be handicapped without it, as would Governments and their militaries. Later, as we learned to transmit more complex information, voice, data, etc., the modulation process became more complicated. Amplitude modulation, or AM, means to make the carrier stronger or weaker in unison with the modulating information and frequency modulation, or FM, means to change the frequency of the carrier higher or lower with the modulating information. These sidebands take up space in the spectrum and many modulation techniques to conserve space are being used. This philosophy is termed - Narrow Band Transmission.