Phase-shift keying (PSK) is a digital modulation technique used to transmit data by changing the phase of a carrier wave. In PSK, the phase of the wave is altered to represent different data values, allowing for efficient communication over various media. Each unique phase corresponds to a specific bit pattern, enabling the receiver to decode the transmitted information. There are several variations of PSK, including binary phase-shift keying (BPSK) and quadrature phase-shift keying (QPSK). BPSK uses two phases to represent binary data, while QPSK uses four phases, effectively doubling the data rate. This makes PSK a popular choice in applications like wireless communication and satellite transmission.