A Lloyd-Max quantizer is an optimal quantization method used in signal processing that minimizes the mean squared error between the original continuous signal and its quantized version. It works by determining the best way to partition the signal's range into discrete intervals and assigning values to those intervals to achieve the highest possible fidelity in the reconstruction of the original signal. This technique is particularly important in analog-to-digital conversion, where the goal is to efficiently represent continuous signals with a finite number of discrete levels.