1）what = the thing which；whatever = anything
　　　what you want has been sent here.
　　　whatever you want makes no difference to me.
2) who= the person that　 whoever= anyone who
　　 （錯(cuò)）who breaks the law will be punished.
　　 （錯(cuò)）whoever robbed the bank is not clear.
　　 （對(duì)）whoever breaks the law will be punished.
　　 （對(duì)）who robbed the bank is not clear.
3) that 和 what　
　　當(dāng)that引導(dǎo)定語(yǔ)從句時(shí) ，通常用作關(guān)系代詞，而引導(dǎo)名詞性從句時(shí)，是個(gè)不充當(dāng)任何成分的連接詞。賓語(yǔ)從句和表語(yǔ)從句中的that�？墒÷�。what只能引導(dǎo)名詞性從　句， 用作連接代詞，作從句的具體成分，且不能省略。
　　i think (that) you will like the stamps.
　　what we need is more practice.