You must have heard the quote written by William Shakespeare:
"All the world's a stage, and all the men and women merely players: they have their exits and their entrances; and one man in his time plays many parts, his acts being seven ages."
As per my interpretation, he wanted to say that this world is like a stage, and human beings are like players or actors who perform our role in it. Every actor may have his own discrete personality and influence, but there is only one stage, with a finite area, predefined props, and lighting conditions.
In the same way, a world in PhysX is known as scene and the players performing their role are known as actors. A scene defines the property of the world in which a simulation takes place, and its characteristics are shared by all of the actors created in the scene. A good example of a scene property is gravity, which affects all of the actors being simulated in a scene. Although different actors can have different properties, independent...