planet Earth and all life upon it, including human civilization
World usually means a planet. When people say "the world" they usually mean the planet Earth. Humans and all other known living things live in this world.
Before people discovered that Earth is a planet, they often used "World" to mean "Universe". They still sometimes use it to mean all humans or all civilization. Sometimes they mean an even smaller part of Earth such as Western world or Islamic world or third world.
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