The term 'Which Person' is used to refer to two different words: WHO and WHOM. WHO is a three-letter pronoun used to ask questions about the identity of a person, while WHOM is a four-letter pronoun used to ask questions about the object of a preposition. Both pronouns are used to refer to people, but WHO is used when the subject of the sentence is the person being referred to, while WHOM is used when the object of the sentence is the person being referred to. For example, if you were asking 'Who ate the last cookie?', you would use the pronoun WHO because the person who ate the cookie is the subject of the sentence. On the other hand, if you were asking 'To whom did you give the last cookie?', you would use the pronoun WHOM because the person who received the cookie is the object of the sentence.