For centuries, Europeans have explored places unfamiliar to them. The big push to explore happened from the 1400s to the 1600s and is known as the Age of Discovery or the Age or Exploration. Here are some sites that will help you learn more about individual explorers, the places they went, and the tools they used to get there.
For a broad website on exploration that includes biographies of explorers, information and illustrations ships and navigation tools, plus an interactive map showing voyages of the most ancient explorers through the 1920s, check out Exploration Through the Ages from the Mariners Museum. Here's another link to exploration info at the museum.