And if today we know our Earth better than in the days of antiquity, then this is the merit of brave navigators, courageous pioneers and tireless researchers. Their adventures are described in this volume "What is What." Despite the dangers that lay in wait, real or imagined, they boldly rushed into the unknown, where their thirst for fame and military honors, a desire to find gold, precious stones and exotic spices, open new trade routes, and introduce other peoples to their faith attracted them.