256-QAM is a digital signal modulation technology that encodes eight bits of information into every LTE signal sent from the tower to your device, instead of the typical six bits with 64-QAM. That results in up to 33% faster download speeds. It also means that you need fewer resources from the tower to complete your downloads, since more data is being sent to you in every signal. In the highway analogy, it would be akin to stuffing 33% more packages into each delivery truck, reducing the number of trucks on the road and improving speeds for everyone.