QPSK, or Quadrature Phase Shift Keying, is a digital modulation technique used in communication systems. It encodes data by varying the phase of a carrier wave, allowing the transmission of two bits of information per symbol. This efficiency makes QPSK suitable for applications like satellite communications and wireless networks. In QPSK, there are four distinct phase shifts, each representing a unique combination of bits: 00, 01, 10, and 11. By using these phase shifts, QPSK can transmit data more efficiently than simpler modulation schemes, such as BPSK (Binary Phase Shift Keying), which only conveys one bit per symbol.