FPU stands for Floating Point Unit. Back in the dark ages, when CPUs had fewer than a million transistors, most computers had no built-in ability to do math with floating point numbers. They had to simulate floating point math using clever combinations of integer math. Power users could buy an extra chip, essentially a second CPU, to do their fancy arithmetic for them. These separate units were called floating point units. Thankfully, those barbaric days are past and virtually all new computers come with a built-in floating point unit.