Social Darwinism was a theory that applied the principles of natural selection to social relations. Charles Darwin had demonstrated that species evolved through selective adaptations that made them better able to survive and reproduce. Social Darwinists characterized human relations as a struggle, with the implication being that those who were successful in business or in other pursuits were so because of their inherent superiority. Generally, Social Darwinism was associated with a laissez-faire approach to business. This included opposition to anti-trust legislation, workplace regulations, minimum wage laws, and other measures. Providing relief to the poor, for instance, was construed by many Social Darwinists as weakening humanity in the long term. Social Darwinism was also related to many of the racial theories that emerged in the late nineteenth century. Non-whites were understood as inferior, and this belief was used to justify segregation as well as anti-miscegenation laws. Social Darwinism also influenced the pseudo-science known as eugenics, which advocated the elimination of "bad genes" from humankind through sterilization, selective marriage, and other methods. Social Darwinism contributed to calls for empire by some who viewed geopolitics as a vast struggle between nations, and it could obviously be used to justify war, both as a way for "superior" men to be challenged through struggle and as a reflection of the natural order of things.
Social Darwinism was an ideology or philosophy that tried to apply Darwinian evolutionary principles to society, and day to day social/political life and also to sociology, economics and politics, often insisting on a 'survival of the fittest' system and trying to prove that on this basis, some societies/people/groups/races etc,. were in fact, 'superior' to others.
Historically speaking, from the 1870s to modern times, such 'biological' concepts were persistently applied to the areas mentioned above, although the term itself was only applied much later, during the 1940s.
In recent times, too, the basic premises of Social Darwinism has supported and helped promote (on the one hand) a 'laissez faire' capitalism and competitive environment, with little or no room for public altruism; and (also, on the other hand) in political terms, brought forth such unpleasant doctrines as Fascism, Nazism/anti-Semitism, eugenics, colonialism/imperialism, ethnic and class/social discrimination etc.
Social Darwinism is the belief that the fittest survive in both nature and society. Wealthy business and industrial leaders used this concept to justify their success.