Our Dreams Have Many Purposes, Changing Across the Lifespan

Dreams differ not only across a single lifetime or a single night, they also differ dramatically across historical epochs. The dreams of the ancient Greeks and Romans, and indeed the dreams of most peoples of the ancient world, were viewed as direct portals into the spirit world and the realm of the ancestors and gods. Ancient peoples (and traditional peoples even today) often experienced dreams as the place to conduct a transaction with a spirit being who could significantly help or hinder you in your daily affairs.

Source: aeon.co