The Neural Net CPU is a "learning computer" and one of the most powerful microprocessors ever built. All of the battle units deployed by Skynet contain a Neural Net CPU. Housed within inertial shock dampers within each battle unit, the CPU gives Skynet the ability to control it's units directly, or allow them to function by themselves, learning from a pre-programmed knowledge base as they go. This means that each battle unit has the potential to adapt to its situation, and literally reason through problems and tactical maneuvers. In the case of the various Terminator series, this means that they can learn to behave more like humans in order to be better equipped for infiltration.