Navigation
An example of people who used the stars were the Vikings.  They knew that the star called Polaris (the North Star) does not change location and points to the north. They would then know the latitude (distance from the equator), by measuring the angle between Polaris and the horizon. They also used animals, especially birds, to know if land was nearby. They also knew that specific kind of clouds form near land and that waves are different near land than at high seas.