This comes from the early days of radio communications and is the traditional amplitude modulation by an analog signal like human voices. It is also short for Double Sideband Suppressed Carrier or DSBSC. The latter is just multiplying the audio signal by the carrier sinewave. This is not used much any more now that filtering and phasing methods of generating SSBSC are inexpensive, but it was mostly on HF for voice communications. It has about 6 dB SNR improvement over AM.