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

What are you want to buy 是病句。

What are you want to buy 这种说法就是错误的！！！

区别:一个是错的，一个是对的。。

"What are you want to buy" = 不正确。语法错误.
"What do you want to buy" = 正确.

"are" = verb to be = 用名词
e.g. "Are YOU a boy?"

"do" = verb = 用动词
e.g. "Do you GO to school?"

第一句是错的。除非你说what are you wanting to buy?但英语是没有这种说法的。通常是采用后面那一种。或者口语化：what do you wanna buy?
注：wanna=want to