The Age of Exploration was a period of extensive overseas travel which began in Europe in the fifteenth century. Historians have identified a number of reasons for this sudden interest in exploration, beginning first with the Christian desire to save souls. This had really started with the Crusades, which began in the eleventh century, but was driven further by the idea of Prester John. He was allegedly a Christian king with lands in the East who urged those in the West to come and join him in converting the non-believers. While Prester John did not actually exist, it encouraged many Europeans to try and find him, especially the Portuguese.
Economically, the Europeans wanted to explore because they believed that faraway lands, particularly in the East, were places of vast wealth and riches which they wanted to claim. This was a strong motivating factor for the Spanish who became very preoccupied with the idea of finding gold and silver.
Finally, another reason for European exploration is the growth of imperialism. The desire to create an empire was at its height in the fifteenth century. Moreover, thanks to improved naval technology, the Europeans were physically able to go out and conquer new lands, just like their Ancient Roman and Greek predecessors.