Describe Charles Darwin’s theory of evolution in your own words. How does it differ from Herbert Spencer's idea of Social Darwinism?

I'm not an expert on this but I believe that Darwin felt evolution happens by natural selection. That is Individuals in a species show variation in physical characteristics over a very long time period. Only the strongest versions of a species survive. Spencer believed that human evolution has as much to do with social classes and culture as it has to do with biological changes.