Porsche’s rear-wheel steering system isn’t particularly revolutionary; Honda’s humble Prelude featured it in the late 90s.
However, while Prelude only used it to reduce the cars turning circle, the 911 uses for to improve high speed stability as well as improved agility. Essentially, the rear wheels allow the 911 to modify its effective wheelbase. Having the rear wheels turn in the same direction effectively reduces the cars wheelbase for increased agility. Those clever Germans; check out Porsche’s own explanation below: