Rear-wheel steering is nothing new on a Porsche, or any sports car for that matter, but if you wanted to know how it works and what it does then check out this official video.
Basically, at low speeds the rear wheels turn in the opposite direction to the fronts, in order to boost maneuverability and reduce the amount of steering lock you have to apply. As speed builds, they switch to turning in the same direction to the front wheels in order to boost high speed cornering stability.
Porsche calls the effect it has “a virtual wheelbase extension,” and we cannot argue against the explanation – that’s exactly what such a system feels like from behind the wheel.
It works exactly like the 4Control system employed by Renault in its latest Megane GT or some versions of the Acura RLX (Honda did try it before in the 1980s, so it has the experience).