Why is Spencer's theory is an Evolutionary Theory. Was Spencer interested in social reforms? What would Spencer do about poverty in our society, given his views on social reforms?

Spencer's theory of "survival of the fittest" is a kind of evolutionary theory. After reading Darwin's On the Origin of Species, Spencer applied some of the ideas of natural selection to the realm of sociology. He believed that groups, which he called "favored races," that possessed advantages would be most likely to survive. Though he applied aspects of natural selection to his ideas, his theory also has elements of Lamarckism, the (erroneous) concept that people can pass traits that they acquire after birth to their offspring. Spencer's theories were applied to sociology and became known as "Social Darwinism," a school of thought that inspired industrialists such as Andrew Carnegie. 
Spencer was a philosopher, not a social reformer. His theories justified the kind of laissez-faire capitalism that developed during the Industrial Revolution, and his theories explained that industrialists such as Andrew Carnegie should be at the top of the economic and social pyramid while others struggled below. Spencer's view on today's poverty would likely be that the economic situation is justified by the fact that those who are fittest have risen to the top, while those struggling in poverty should do so. That way, the poor may not be as likely to reproduce and pass along undesirable characteristics. Spencer was not sympathetic to the poor or working classes.