What is the difference between race and ethnicity?

Actually your question is not stupid. there is only but one race & that is human race. There are different divisions of the human race...sorta like animals. Example: dogs are dogs, but there are many different breeds of dogs. The same is for the human race, we are all related. Ethnicity comes from a certain group of people in a certain area that has for a long time married & had children within that one group / tribe etc.