Christopher Columbus (1451?-1506) was a probably Genovian sailor who crossed the Atlantic in service of Spain. He is often credited as the discoverer of the Americas, and although he was not the first European to reach America (at least the Vikings were there before), it is indeed his voyages that created the still-existing link between the continents.
Columbus was convinced that it would be possible to reach the Indies (India, Indonesia and other areas in south and east Asia) easier by sailing west and crossing the Atlantic than by going around Africa. He laid down his plans to the king of Portugal, but was refused - his experts believed that the route would be longer than Columbus thought (the actual distance was even longer than the Portuguese believed). Columbus then tried to get backing from Spain or some other country, and finally in 1492, when they had conquered Granada, the last Muslim stronghold on the Iberian peninsula, the Spanish king and queen, Ferdinand and Isabella, agreed to have an expedition sent out.
Still in that same year, Columbus left with three ships, the Santa Maria, Nina and Pinta. He crossed the Atlantic from the Canary Islands, and landed on an island on the other side. There is still much discussion about which island this was (see http://www1.minn.net/~keithp/cclandfl.htm), but at least it is quite certain that it is one of the Bahamas. On this first voyage, Columbus also discovered Cuba and Hispaniola, on which he left some colonists.
Columbus and his discoveries at one stroke became famous, and he soon left for his second voyage (1493-6). He had a course more southerly than on his first voyage, and landed on Guadeloupe. He discovered a few more of the Minor Antilles and Puerto Rico, then went to Hispaniola, where his colonists had disappeared. He built a new, larger colony, and started the conquest of the island. Before leaving back to Europe, he explored the south coast of Cuba (which he thought was a part of the mainland) and discovered Jamaica.
In 1498, Columbus left for the New World a third time. This time he discovered the island of Trinidad and the mainland of South America with the Orinoco River, before turning to Hispaniola. In 1500, after rumours of mismanagement, he was arrested and taken back to Spain.
Although he regained his freedom, he did not regain his prestige. Nevertheless he made a fourth voyage, in 1502-1504. In this voyage, he explored the coast of Central America from Belize to Panama, but got marooned on Jamaica. He managed to get to Hispaniola to get help.
In 1506, Columbus died in Spain, still convinced that his discoveries were along the East Coast of Asia.