Frequency Shift Keying (FSK) is a digital modulation technique used to transmit data by varying the frequency of a carrier wave. In FSK, different frequencies represent different binary values, typically 0s and 1s. This method is commonly used in applications like modems and radio communications due to its robustness against noise. There are two main types of FSK: binary FSK (BFSK), which uses two frequencies, and multi-level FSK, which can use more than two frequencies for higher data rates. FSK is favored for its simplicity and effectiveness in maintaining signal integrity over long distances.