“Whom” is a word that exists. It’s a word that people have it would appear mostly all but forgotten about. Maybe who cares but here’s the word “whom” for those who do.
To explain its usage, primarily when to use it, I’m going to create a scenario. Most people think “who” is adequate for any time any sentence don’t matter. This is not true though in a technical sense. In a technical sense “who” is used when designating a subject and “whom” is for the object.
Example……
[He] → (subject) went to [the park] → (object)
[The park] → (subject) is where [he] → (object) went.
With that understood, let us move to our “whom” story. In this story, a thing has been done. This thing done has been done by Jack… the sneaky devil! Jack does not make a direct appearance in our tale, however. The main characters of our story, Loraine and Jasmine, they don’t know who did the thing. Our scene opens on their discovery of the thing done…..
Loraine and Jasmine returned from their usual trip to town only to open the front door and be forced to bear witness to the aftermath of the incredible act.
“Who did this?” Asked Loraine.
“I haven’t a clue!” Replied Jasmine.
Jasmine began to move towards the far side of the room to get a closer view. As she came upon it she continued looking, eyes locked unable to peel them away, with Loraine still standing at the door.
Jasmine then exclaimed, “I bet I know! I’ll bet anything it’s was that damned Jack!”
With Jasmine standing a bit of a ways off and facing away from Loraine, Loraine was unable to make out the name clearly.
“Did you say Matt? Say again, you think this was done by whom?” Hollered Loraine.
“It was Jack who did it.” Said Jasmine as she turned her shoulder slightly toward Loraine.
“Ah, of course.” Whispered Loraine.
Okay, now to examine what’s going on here. So we know Jack did it, naturally he did it. To take Loraine’s original question of “who did this” we can substitute Jack for who. And then to take Loraine’s later question of “this was done by whom” we can again substitute Jack in but this time in the place of whom. For it was Jack that did it, and it was done by Jack.
In conclusion……
[Who] → (subject) did [it] → (object)
[It] → (subject) was done by [whom] → (object)
[Jack] → (subject) did [it] → (object)
[It] → (subject) was done by [Jack] → (object)
It’s a matter of how a sentence is structured but how it’s structured is going to determine whether you use the word “who” or “whom.”
My dissertation on “whom.”
p.s. it’s tough I know