Secularization, the process by which religion loses social significance, is a key concept in modern sociology. It involves the separation of religious and government institutions, rationalization of beliefs, and privatization of religious practices. These changes have profound impacts on society's structure and individual worldviews. Historical factors like the Enlightenment, Industrial Revolution, and rise of nation-states have driven secularization. Theories from sociologists like Weber and Durkheim explain how modernization leads to religious decline. However, challenges to secularization theory and varied impacts across societies complicate our understanding of this phenomenon.