Quadrature Phase Shift Keying (QPSK) is a digital modulation technique used in communication systems to transmit data efficiently. It encodes information by varying the phase of a carrier wave, allowing four distinct phase shifts, each representing two bits of data. This enables QPSK to transmit twice the amount of information compared to simpler modulation schemes like Binary Phase Shift Keying (BPSK). QPSK is widely used in various applications, including satellite communications, wireless networks, and digital television. Its ability to maintain a robust signal in noisy environments makes it a popular choice for high-speed data transmission, balancing efficiency and reliability in modern communication systems.