"Who" is a subject pronoun (just like: he, she, you, etc). It is always the subject of a verb. ex: Who turned the light off? (Quien?)- the ''who'' is the subject of the verb. Who told you that? Who broke the lamp? Whom - subject, this is not the recipient of the action, never the subject of action. ex: Whom did you see yesterday? (A quien?) - 'you' is the subject of the verb. You spoke to whom, on the phone? **After prepositions (by, whom, to, etc) Always use ''whom'' ex: This is the person to whom I spoke yesterday. Whom did you watch the movie with? See these two used together. Who kissed whom? Who is teaching whom here? :)

"Who" is the subject; "Whom" is the object.

Who is the subject word and whom is the direct object word. "Who is driving the car?" "By whom is this book?" Even most native speakers fail to use whom when they should. Maybe it will fall out of use altogether.

It is pronoun set: subject, possessive, object. He. His. Him. She. Hers. Her. I . My, Me. Who. Whose. Whom

saying "for who" is incorrect