Amplitude Shift Keying (ASK) is a type of digital modulation technique used to transmit data by varying the amplitude of a carrier wave. In ASK, the presence of a signal is represented by a higher amplitude, while the absence of a signal is indicated by a lower amplitude. This allows for the encoding of binary data, where '1' and '0' are represented by different amplitude levels. ASK is commonly used in applications such as radio communication and optical communication. Its simplicity makes it easy to implement, but it is also more susceptible to noise and interference compared to other modulation techniques like Frequency Shift Keying (FSK) or Phase Shift Keying (PSK).