Answer:
On the planet there is a limited production capacity of resources, as well as a limited availability of them according to the territory in which they are located. Thus, for example, desert places lack aquifer resources, which makes it difficult for the populations that are there to have access to drinking water. But at the same time, in many territories there is an overproduction of a certain resource, such as oil in the Middle East.
In this way, each territory ends up having on the one hand more than it can consume of a certain resource, while on the other there is a shortage with respect to others. For this reason, territories have to opt for trade, with the aim of exchanging surplus resources (because they produce them on a large scale) for those products that they lack. This encourages commercial exchange, and generates an economic interdependence between nations, which in turn choose to produce more resources on which they can later trade.
