Eraser Head is a slur used to describe Blacks in a derogatory way. During the late 80's and early 90's it was popular for blacks to cut their hair at an angle, forming a bevel that look similar to those pink erasers that you used in grade school.
The word Eraser Head is a racial slur that has been used historically to degrade and dehumanize blacks. The word is still used by some people for this purpose, and it is seen as offensive and hurtful to blacks. If you are unsure about whether or not it is appropriate to use the word Eraser Head, it is best to err on the side of caution and avoid using it in any situation.