What does James Rachels mean by “cultural relativism,”

What does James Rachels mean by “cultural relativism,” and how does he argue against cultural relativism in the sections of the article entitled “The Consequences of Taking Cultural Relativism Seriously,” “Why There Is Less Disagreement Than It Seems,” and “How All Cultures Have Some Values In Common”? Write this paper carefully, as if you are explaining this to a friend who has never taken an ethics course. Make sure it is entirely in your own words (unless you quote Rachels directly). Whenever possible, use examples of your own, rather than Rachels’ own examples.