Complex sentence: PhysX is a proprietary realtime physics engine middleware SDK developed by Ageia (which itself was acquired by Nvidia in February 2008) with the purchase of ETH Zurich spin-off NovodeX in 2004.
Split into simpler sentences: PhysX is a proprietary realtime physics engine middleware SDK. It was developed by Ageia with the purchase of ETH Zurich spin-off NovodeX in 2004.