ELI5 when to use 'who' vs 'whom'

If you're a fan of language as well as NBC's "The Office," you have to admire the grammar lesson cleverly written into last week's episode, "Money."
Called into a meeting, the fictional staff at Dunder Mifflin's Scranton, Pa., branch veers off on a long and confusing tangent about the use of who or whom. Typically clueless boss Michael tries bluffing his way through the puzzle, but practical and smart receptionist Pam and proper HR specialist Toby lead the staff to the correct grammar rule in the dialogue below:
Ryan: You know what I really want? What I really want is for you to know (the computer system) so you can communicate it to your people here, to your clients, to whomever ...
Michael: (Snort) OK.
Ryan: What?
Michael: It's whoever not whomever.
Ryan: It's whomever.
Michael: No. Whomever is actually never right.
Jim: Well, sometimes it's right.
Creed: Michael is right. It's a made-up word used to trick students.
Andy: No. Actually, whomever is the formal version of the word.
Oscar: Obviously, it's a real word, but I don't know when to use it correctly.
Michael (to camera): Not a native speaker.
Kevin: I know what's right. But I'm not going say, because you're all jerks who didn't come to see my band last night.
Ryan: Do you really know which one is correct?
Kevin: I don't know.
Pam: It's whom when it's the object of a sentence and who when it's the subject.
Phyllis: That sounds right.
Michael: Sounds right, but is it right?
Stanley: How did Ryan use it, as an object or a subject?
Ryan: As an object.
Kelly: Ryan used me as an object.
Stanley: Is he right about that ... ?
Toby: It was: Ryan wanted Michael, as the subject, to explain the computer system, the object, to whomever, meaning us, the indirect object, which is the correct usage of the word.
Most of us can identify with Oscar: We know there's a rule, but we're not quite sure. Trust Pam. Trust Toby. Laugh at Michael and, well, pretty much every other character in this scene.
You can view the entire hour-long episode at http://www.nbc.com/. And, of course, you can catch a new episode of "The Office" at 8 tonight on NBC.
Cindy Eggert is the Journal Sentinel assistant day copy desk chief.
/r/explainlikeimfive Thread