The world is the planet Earth and all life upon it, including human civilization. In a philosophical context, It is the whole of the physical Universe, or an ontological world. In a theological context, It is the material or the profane sphere. As opposed to the celestial, spiritual, transcendent or sacred. The "end of it" refers to scenarios of the final end of human history, often in religious contexts.
History of the it is commonly understood as spanning the major geopolitical developments of about five millennia, from the first civilizations to the present. In terms such as it's religion, language, government, and war, It suggests international or intercontinental scope without necessarily implying participation of the entire world.
It's population is the sum of all human populations at any time; similarly, economy is the sum of the economies of all societies or countries, especially in the context of globalization. Terms like world championship, gross product, flags imply the sum or combination of all current-day sovereign states.