explain the developments in Europe and Africa that led up to Columbus's voyage to America

Europeans began to explore after Marco Polo returned with stories of China and its riches. First, they they went Africa where they colonized and used African slaves as plantation workers. Vasco da Gama reached India in 1498, which opened a sea route to the Far East. The dangers of this sea route influenced Christopher Columbus to sail to the west.  Because of this, he "discovered" the Americas. Although the Portuguese were first colonists in America, the Spanish became the dominant nation.