Who
--> Who refers to the subject (the person performing the action)
--> कौन (the doer)
Example:
In questions:
1) Who ate all the apples?
2) Who took my keys?
3) Who is at the door?
4) Who needs a paper?
In direct questions and statements -
1) Can you tell me who the owner is?
2) She asked me who was on duty?
To introduce relative clauses -
1) The suspect is the who who is wearing a grey shirt.
2) She is the woman who owns this hotel
Whom
--> Whom refers to the object (the person receiving the action)
--> किसे/किसको: The receiver
Example:
As the object of question -
Whom did the committee appoint?
With prepositions -
1) Send it to whom it may concern.
2) Tell us where you went and with whom?
When preceded by quantifiers: (all, most...)
the girls, all of whom were alive, were found.
In relative clauses:
She gave bith to boy whom she called Sam.