AM
A (radio) modulation method whereby a high frequency (RF) carrier-frequency is modulated by a lower baseband signal (AF) - the modulating signal.
The 'carrier' itself does not fluctuate in amplitude; the (transmitted) carrier-baseband product produces an envelope of the carrier-wave whose amplitude varies at the rate of the modulating signal.
Over-air and at the receiver, the modulating data appears in the form of signal components at frequencies slightly higher and lower than that of the carrier.