An eraser is an item used to remove the marks left by pencils and some types of pens. Modern erasers come in all colors, and may be made of rubber, vinyl, plastic, gum, or similar materials.
Erasers pick up graphite particles, thus removing them from the surface of the paper. Basically, the molecules in erasers are ‘stickier’ than the paper, so when the eraser is rubbed onto the pencil mark, the graphite sticks to the eraser preferentially over the paper.
Some erasers damage the top layer of the paper and remove it as well.
Erasers attached to pencils absorb the graphite particles and leave a residue which needs to be brushed away. This type of eraser can remove the surface of the paper.
Soft vinyl erasers are softer than the erasers attached to pencils, but are otherwise similar.
Art gum erasers are made of soft, coarse rubber and are used to remove large areas of pencil marks without damaging paper. These erasers leave a lot of residue behind.
Kneaded erasers absorb graphite and charcoal without wearing away. Kneaded erasers may stick to the paper if they are too warm. They eventually pick up enough graphite or charcoal that they leave marks rather than pick them up, and need to be replaced.