These are the routine ways of travel by which goods are exchanged, including both land and sea.

The routine ways in which goods are exchanged were known as trade routes, they were routes such as the triangular trade route in the Atlantic ocean, where many diverse types of good were traded among merchants. The silk road is a very good example of a strong trade route that shaped history, it allowed contact of many nations around the world, allowing for different influences to spread, particularly western influence/ thinking.

The theory is land mass basically what they said.