If the rod and ball are now brought near one another, things start to happen.
The electrons in the ball feel the net negative charge on the rod. They try to run away toward the far side of the ball. The ions would like to move toward the rod, but they bound to one another and cannot move.
This shifting of charges within an object is called polarization.
We end up with two forces on the ball: A repulsive force on the electrons. An attractive force on the ions.