Why conflicts with our idea of moral progress.

Why Moral Relativism conflicts with our idea of moral progress. 
What is the main idea (general definition) of Moral Relativism? What examples of cultural differences are often cited in support of Moral Relativism? What is a general definition of moral progress? What are some of the examples of moral progress discussed in your textbooks? How do these examples of moral progress pose a problem for Moral Relativism?