The original position is the perspective that a hypothetical creator of a society must adopt in order to ensure that the society will be just.
Rawls argues that a just society would be one that was devised by someone who was in the original position. This person would have to set up the society without knowing what position he or she would have in it. Such a person would set up a society where even the poorest and least privileged people would have basic rights and would have enough to live on. The person in the original position would do this because he/she might potentially end up with the lowest status in the society.
The original position, then, is the perspective of the hypothetical person who is creating a society but does not know what place he or she will hold in that society. Of course, this is not meant as a description of something that has actually happened in human history. Instead, it is meant as a way of evaluating the justice of a given society's basic systems.