Where are you from
=Where do you come from
你来自哪里?（你可以回答一个国家,或一个城市,或一个小地方）
问的意思相同.只是你的回答不同.
第一个句子回答I am from China.
第二个句子回答I come from China.
what nationality are you?
=What is your nationality?
你的国籍是什么?
你是哪国人?（你只能回答你的国籍,国家）
你可以回答：I am a Chinese.
或 Chinese is my nationality.
My nationality is Chinese.
I have Chinese nationality.