Which type of transmitter modulation changes the amplitude of an RF wave for the purpose of conveying information?

The term itself gives away the answer: 'Amplitude Modulation' (AM) modifies the amplitude—which is the strength, peak voltage, or size—of the radio frequency (RF) carrier wave to carry information such as voice. In this process, the frequency and phase of the carrier wave remain constant, while its amplitude fluctuates in direct proportion to the audio signal being transmitted. Distractors like Frequency Modulation (FM) and Phase Modulation (PM) keep the amplitude constant while varying the timing (frequency or phase) of the wave, and Frequency Shift Keying (FSK) shifts between two distinct frequencies for digital data.