In the days leading up to the magnetic compass, European explorers would rely on star constellations as a form of navigation. As you can probably imagine, it was probably quite difficult to navigate on open water by looking at the stars, especially since star positions varied in appearance in accordance to Earth's position. Once the magnetic compass was starting to be used, explorers were less likely to get lost out at sea, thus creating the opportunity to explore new places, establish colonies, and begin trade and commerce of previously scarce or unavailable goods. I hope this helped !