Scientific racism is the idea to use science to promote racism. This is different from using the scientific method, and simply pointing out differences between races. The scientific method does not claim that one race is "better" than another, it may simply show differences between the races.
Very often, the term is also used for different theories of anthropology and other closely-related disciplines to create evidence, which would allow to classify humans into groups. These groups are then called "races", and some think it is possible to claim that one race is superior to another. Most of these theories were common between 1880 and 1930, in a period called New Imperialism.