Why are we different?

Race it is just a word. A part of language. Does race really difine who you are? While your watching this vedio I would like you to think about:
What realy is race?
Does it difine a person?
I think it doesn't. why should someone be judged on a physical feacture they cant change? No one can change where they come from or what ethnic group they belong to. So why is race so important?