The prompt for this topic is rather straightforward and deliberately argumentative. In the simplest sense what you need to do is "pick a side" on this topic (for or against or anything in-between) and then defend it. The prompt:
Do you accept ethical relativism as an adequate explanation of the essential nature of human morality? Why or why not?
This, like most we will discuss, is not a small topic and you will need to set limits to what you plan to address--but the goal should be very clear. Remember that if you do not turn it in by that deadline then you cannot write on this topic.
The sort of qualities I will be looking for when grading include (1) clarity of writing, (2) accuracy of your statements and thoroughness of the explanations (that is that it is clear you understand what is at issue here) and (3) the reasonableness of your arguments.