This document discusses different types of modulation techniques. It describes analog modulation techniques including amplitude modulation (AM), frequency modulation (FM), and phase modulation (PM). AM varies the amplitude of the carrier signal based on the message signal. FM varies the frequency of the carrier signal linearly with the amplitude of the message signal. PM changes the phase of the carrier signal based on the message signal. The document also briefly introduces digital modulation techniques, noting they are similar to analog modulation but operate on discrete amplitude levels for binary digital signals using amplitude-shift keying, frequency-shift keying, or phase-shift keying.