The stars have always helped people at night get to distant places. On the sea, sailors did eventually have tools to use to find their way to their destination. Knowledge of the stars and their locations in the sky helped Greek sailors figure out which direction was North, South, East, and West.
Over time, the astrolabe was invented where this tool used the stars to show the direction. Again, the stars helped find directions even though a tool was used. The North Star is the brightest star. Many sailors would try to find this star because it would shine the brightest in the night sky. They would then realize which way was North. Having this information about the location of the stars was just as important for the Greek sailors as their sailing skills.