Moral relativism may be any of several philosophical positions concerned with the differences in moral judgments across different people and cultures. Descriptive moral relativism holds only that some people do in fact disagree about what is moral; meta-ethical moral relativism holds that in such disagreements, nobody is objectively right or wrong; and normative moral relativism holds that because nobody is right or wrong, we ought to tolerate the behavior of others even when we disagree about the morality of it.
Not all descriptive relativists adopt meta-ethical relativism, and moreover, not all meta-ethical relativists adopt normative relativism. Richard Rorty, for example, argued that relativist philosophers believe "that the grounds for choosing between such opinions is less algorithmic than had been thought", but not that any belief is as valid as any other.
Moral relativism has been debated for thousands of years, from ancient Greece and India to the present day, in diverse fields including philosophy, science, and religion.
Descriptive moral relativism is merely the positive or descriptive position that there exist, in fact, fundamental disagreements about the right course of action even when the same facts hold true and the same consequences seem likely to arise. It is the observation that different cultures have different moral standards.
Descriptive relativists do not necessarily advocate the tolerance of all behavior in light of such disagreement; that is to say, they are not necessarily normative relativists. Likewise, they do not necessarily make any commitments to the semantics, ontology, or epistemology of moral judgement; that is, not all descriptive relativists are meta-ethical relativists.
Descriptive relativism is a widespread position in academic fields such as anthropology and sociology, which simply admit that it is incorrect to assume that the same moral or ethical frameworks are always in play in all historical and cultural circumstances.