Prius Prime is a Plug-In Hybrid model, meaning it switches from electric to gas when your battery runs out.
Prius is a Hybrid model, meaning that the gasoline engine and the electric motor are separate from each other. The Prius will use electric when at slow speeds, both gasoline and electric when accelerating,
and gasoline when full force is applied to the accelerator. Hybrids cannot be plugged in, the batteries are regenerated by capturing energy from deceleration that's typically lost to heat generated by the brakes in conventional cars.