Quantization noise is the error introduced when a continuous signal is converted into a digital signal. This occurs during the quantization process, where the infinite range of values is mapped to a finite set of levels. The difference between the actual signal and the quantized signal results in noise, which can affect the quality of the digital representation. In practical terms, quantization noise can lead to distortion in audio and visual signals, impacting the fidelity of recordings and transmissions. Techniques such as dither can be employed to minimize the perceptibility of this noise, enhancing the overall quality of the digital output.