Catherine the Great changed Russia primarily by westernizing the country, adopting Western culture, ideas, and technology. Under her rule, she implemented various reforms that modernized various aspects of Russian society, government, and the economy. Additionally, she also expanded (or added) more land to Russia, significantly increasing its territory through military conquests and the annexation of several regions.
Both of these responses highlight key aspects of her impact on Russia, but the emphasis on westernization is particularly significant in terms of changing the cultural and social fabric of the nation.