The term 'Roof of the World' is used to refer to two different geographical locations. The first is Tibet, which is a region in Asia located between India and China and is known for its high altitude and rugged terrain. The second is the Himalayas, a mountain range that stretches across much of South Asia and is home to some of the world's highest peaks. Both of these locations are known for their extreme elevation, making them the 'Roof of the World'.