Basically, globalization can't be explained in full in the space we have here. The simple definiton is that the economy is now global, meaning everything is interconnected. You can hardly buy any product without some part of it coming from a global source.
A big reason for globalization has been the advances in technology. You can now be in another country and through the use of available technology do business "face to face" with someone in another country.
Globalization is simply the process in which the world becomes more interconnected. This process affects the world's economies and its societies and cultures as well. Countries come to trade with one another more and more. This obviously links their economies, but it also casues them to have much more contact with one another's cultures. Gradually, this tends to cause cultures to become more like one another.