1.用作连接代词,表示“什么”(由疑问词变来).如：
I don’t know what he gave her.我不知道他给了她什么.
What he will say at the meeting is not known to us.他在会上将说些什么,我们还不知道.
2.表示“……所……的(东西)”,在结构上相当于一个名词加一个定语从句(所以有人称这样用的what 为关系代词型的what).如：
■把你买的东西拿给我看.
Show me what you bought.　→Show me the thing that you bought.
■这是他想要的东西.
This is what he wants.　　→This is the thing that he wants.
■我们需要的是钱.
What we need is money.　→The thing that we need is money.