Social Progressivism is the view that as time progress so should societal morality (from Wikipedia). Social progressives advocate for morality to be based on advancements in Science and philosophy, rather than religious dogma.
Social Progressivism is opposed to Social conservativism. While Social Conservativies advocated to keep slavery, Social progressives opposed it. Social progressives also campaigned for the right to vote for women. Today they advocate equal marriage and a women's right to choose.