what is the difference betwween "town" and "down town"

First notebook entry: Introducing myself I want to learn English,because i think English is more and more important in the world.Also i want to make friends from different countries.My native language is Chinese,and in collage time ,i have learn Japanese for a short time.In my free time ,i like reading books,and travelling.If you have the same hobbies with me ,i think we will be good friends.