This is man who I referred to 区别

This is man who I referred to 区别

who 可以做主语,又可以做宾语
whom 只能做宾语
例子：1,who are you?不能是whom are you?
2,This book belongs to whom/who?两者都可以
1.who指人,在从句中做主语
(1) The boys who are playing football are from Class One.
(2) Yesterday I helped an old man who lost his way.
2.whom指人,在定语从句中充当宾语,常可省略.
(1) Mr.Liu is the person (whom) you talked about on the bus.
(2) Mr.Ling is just the boy whom I want to see.
注意：关系代词whom在口语和非正式语体中常用who代替,可省略
简单点说就是：
Whom 只能出现在从句里面或是介词（如 to,from,at,of..）后面.
1． Whom 出现在从句里面时,所有用whom的地方都可以用who代替.Whom 这个词只出现在很正式的书面语.口语不用.
2． Whom 在介词（如 to,from,at,of..）后面时,不可替换.

一样的意思，只是结构不同，意思一样的