Quadrature Amplitude Modulation (QAM) is a method used in digital communication to transmit data by varying the amplitude of two signals. These signals are typically sine waves that are 90 degrees out of phase, hence the term "quadrature." By changing the amplitude of these two waves simultaneously, QAM can encode multiple bits of information in each symbol, making it efficient for high-speed data transmission. QAM is widely used in various technologies, including Wi-Fi, digital television, and modems. Different variations of QAM, such as 16-QAM or 64-QAM, indicate the number of unique symbols that can be transmitted, allowing for increased data rates while maintaining signal integrity.