There are two different ways to answer this question.
First, we can say that Christopher Columbus had a huge impact on today’s world. It was through his voyages that the New World was “discovered.” This led to many very important changes. First, it led to the destruction of large populations of Native Americans. Large percentages of these people died from diseases and other causes related to the Europeans. Those who survived generally had their societies destroyed and came to be subordinate members of societies dominated by Europeans. Second, it led to the development of African slavery. The “discovery” of the Americas led to the creation of plantations that needed slave labor. This led to the African slave trade. Third, it led to the eventual creation of the United States. This has changed the world because it helped to inspire the growth of democracy in the world and because the US is the world’s foremost power today. None of these things, in this view, would have happened had it not been for Columbus.
Columbus’s voyages also led to less momentous changes, but changes that have nonetheless affected us. These changes include the flow of different foods around the world. For example, we associate potatoes with Ireland and we associate tomatoes with Italian cooking. We associate chili peppers with Indian and Chinese cooking. None of this was true before peppers, potatoes, and tomatoes were brought from the Americas to the rest of the world.
However, we can also say that Columbus had no impact on today’s world. If Columbus had not “discovered” the New World, someone else would have. There is no way that such a huge landmass was going to be undiscovered by Europeans for much longer. In this view, Columbus was just the person who happened to come first. His actions did not truly change the course of history because all of the changes that I list above would have happened even if Columbus had never sailed.