Since you have put this in the Business group, I assume that you are talking about these terms from an economic point of view. From that point of view, globalization is the process of making the world's economy more integrated--the process of bringing more and more parts of the world together into one seamless economy. Regionalization is a process that is generally similar to globalization, but can compete with it to some degree.
The main similarity is that, in both cases, there is a movement towards economic integration of more than one country. In regionalization, you have the countries of a region (say the EU) integrate their economy. In globalization, more than one region is involved.
Although the two are similar, regionalization can be opposed to globalization. This occurs when a region tries to integrate itself, but then puts up barriers against the rest of the world. This would be the situation if, for example, China and the countries of SE Asia integrated but then prevented extensive integration with the rest of the world's economy.