Final answer:
The difference between the original analog signal and the digital signal in digital transmission is known as quantization error, which occurs during analog-to-digital conversion.
Step-by-step explanation:
With digital transmission of analog data, the quantization error is the difference between the original analog signal and the approximated, digital signal. When an analog signal is digitized through the process of analog-to-digital conversion, it is approximated to the nearest value that can be represented by the digital format. This approximation results in some degree of error since the continuous signal must be translated into a finite number of discrete steps. The better the resolution of the digital representation (the more bits used), the smaller the quantization error and the more accurately the digital signal can represent the original analog signal.