The world! It is a word capable of as diverse interpretations or misinterpretations as the thing itself a thing by various people supposed to belong to heaven, man, or the devil, or alternatively to all three.
Basically, GDP is a concept of value added. It is the sum of gross value added of all resident producer units (institutional sectors or, alternatively, industries) plus that part (possibly the total) of taxes, less subsidies, on products which is not included in the valuation of output. Gross value added is the difference between output and intermediate consumption.