Globalization is the process by which the various countries of the world come to be more connected to one another. There are various kinds of globalization. The most famous kind is economic globalization, but cultural globalization exists as well.
Cultural globalization is the process by which countries of the world come to be more culturally similar than they had previously been. In the past, when it was hard to travel between countries or to have much contact with people from other countries, different countries had very different cultures. Now, these differences are eroding. For example, Michael Jackson was a very popular singer in Japan, meaning that Japanese culture had become, at least to some degree, more like American culture. With the rise of YouTube, people in Japan can watch American TV shows. For that matter, the most popular sport in Japan is, arguably, baseball. Japan has that in common not only with the US, but with places like Cuba and the Dominican Republic. All of these things are examples of how culture has become less differentiated than it once was. This is the process that we call cultural globalization.