Kaz is a simulation of the left hemisphere of the brain. He handles data, numeric and linguic information, and uses logic and reasoning. He has difficulty responding naturally to stimuli, and he has nearly no sense of emotions or instinct. (However, since he is an attempt at simulating the human brain, of course he does have some emotional response. But it is nowhere near as heightened.)
Kaz, being closer to the typical idea of a computer, has less features and development than Leopold, and his face and body have far less expressive capabilities. However, since he is able to use language, he acts as the translator between Leo and the scientists. He and Leopold communicate their information through binary (computer language), but externally express it very differently.