1)what = the thing which;whatever = anything.例如：

What you want has been sent here. 你要的動詞都送來了。

Whatever you want makes no difference to me. 不管你要什么，跟我沒什么關系。

2) who= the person that whoever= anyone who.例如：

(錯)Who breaks the law will be punished.

(錯)Whoever robbed the bank is not clear.

(對)Whoever breaks the law will be punished. 王子犯法，與庶民同罪。

(對)Who robbed the bank is not clear. 誰搶了銀行還不清楚。

3) that 和 what

當that引導定語從句時，通常用作關系代詞，而引導名詞性從句時，是個不充當任何成分的連接詞。賓語從句和表語從句中的that?？墒÷?。What只能引導名詞性從句，用作連接代詞，作從句的具體成分，且不能省略。例如：

I think(that)you will like the stamps. 我想你會喜歡這些郵票的。

What we need is more practice. 我們需要的是更多的實踐。