Progressivism is a general political philosophy advocating or favoring more or less gradual social, political, and economic reform. Modern Progressivism emerged as part of a more general response to the vast social changes brought by industrialization.
It is left of center in the political spectrum and is to be contrasted with conservatism on the right and the revolutionary left, the former generally resisting changes it advocates and the latter rejecting its gradualism.
Read more about Progressivism: History