Technically speaking, the word "race" defines a human being's physical variances that are part of a larger group with the same physical traits. Ethnicity is actually a cultural variation. For example, the term "Caucasian" includes most white people who are descended from Europe, going very far back. But amongst those Caucasians, are a wide number of "Ethnicities". Southern European peoples have quite different cultures and even languages than Northern European peoples. The same kind of thing is true of people from the various Asian countries. They are of the same race. But the countries that they come from make them quite different ethnically. This answer would be considered to be a simplistic view. It is actually a whole wide study called "anthropology". There are scholars who work at tracing a group of people from now to their past and vice versa. It is a fascinating area of study.
