What are you want to buy 和What do you want to buy的区别,要说为什么

What are you want to buy最好是说what are the things that you want to buy
这样的话,两句话的区别就是前一句里,what是主语,you want to buy是表语从句；
而后一句what do you want to buy里,what是buy的宾语,
两句话里句子成分不同