What is the most important thing to know about Christopher Columbus ?
The answer to this question is quite subjective, as determining the most important thing about Christopher Columbus would depend upon what you consider to be worth knowing about a person.
That being said, most historians would agree that it is important to know that Christopher Columbus is credited with the (re)discovery of the New World. Though Vikings from Northern Europe had traveled to North America during the 11th century, their settlement was short lived. The attempt to settle at L'Anse Aux Meadows in Canada was complicated by weather and a lack of natural resources the Vikings were accustomed to. Centuries later, Christopher Columbus famously sailed from Spain to South America, beginning a long legacy of colonization in the Americas.
Some other things which might be considered about Christopher Columbus were that he traveled on behalf of the Spanish monarchs Ferdinand and Isabella. They funded his journeys so that he might find the New World and bring back resources for their use. During this time, the spice trade with Asia was both lucrative and a sign of luxury. The Spanish monarchs would have loved the idea of importing rare and unusual goods from a place which was mysterious in the European mind.
There has been an academic movement to understand the implications of Columbus' journeys and to make this knowledge a part of historical studies. Christopher Columbus may be credited as the father of the transatlantic slave trade and he believed that people of color needed the shepherding of white Europeans to become civilized. From his arrival in Hispaniola and South America, he captured slaves to bring back to Spain. Columbus' claiming territory and pioneering exploration of the New World for Europeans lead to the forced conversions of millions of First Nations peoples, the colonization of their lands, and the import of African people as a source of labor.