Who,Whom,which,what,whose are Interrogative Pronoun these are used to ask questions.
|Whom||It uses when the person is object||Whom did you tell about my accident?|
|Who||It uses when the person is subject||Who is taking responsibility to deposit the utility bill in the bank?|
|Which||It uses person or thing and for limited choice||which house you are going to buy?|
|What||It uses to ask about something.||what is your name please?|
|Whose||It uses to show possession||Whose is this sports car?|