This document discusses amplitude modulation and demodulation. It begins with an overview of modulation and then describes different techniques for amplitude modulation including double sideband-suppressed carrier, conventional, single sideband, and vestigial sideband. It defines amplitude modulation mathematically and provides an example waveform. It then discusses the demodulation process, explaining that demodulation is needed to recover the original signal from the modulated carrier wave. It describes the amplitude demodulation process and highlights the importance of rectification to prevent the positive and negative envelopes from canceling during filtering.