[paul.fr]

i have two rubbers, one that erases pencil and another that erases ink. how do they do it?

[eric l]

The rubber that erases ink also rubs away part of the paper.  In fact, the process is not essentially different from erasing with a pen knife or nylon brush.
Erasing pencil with a rubber is closer to washing dirty laundry with some detergent :  the carbon particles from the pencil are enrobed with rubber (or plastic) and this "new" particles do not stick to the paper (lower affinity and too big to penetrate into the pores).

[Karen W.]

Well That was interesting! Eraser JOY.. I did not know that the pencil eraser would roll up the lead, frankly I never thought about where or how it left my paper, just that it did! LOL COOL!