Navratri is a nine-day Hindu festival celebrating the victory of goddess Durga over the buffalo demon Mahishasura, symbolizing the triumph of good over evil. It is marked by fasting, prayers, traditional dances like garba and dandiya, and culminates in Durga Puja in some regions, with specific rituals and colors associated with each day. Regional celebrations vary, including Garba in Gujarat, Durga Puja in West Bengal, and Golu displays in South India.