"whom" is the accusative (objective case) of "who", but as far as I know, it's not used very often nowadays, it's kind of getting old and replaced by "who"
for example(I've found this on another site):
" “The MC was so startled by the neckline that he forgot to whom he was supposed to give the Oscar”
“I wonder whom he bribed to get the contract?”
Here an old gender-biased but effective test for “whom” can be used. Try rewriting the sentence using “he” or “him.” Clearly “He bribed he" is incorrect; you would say “he bribed him.” Where “him” is the proper word in the paraphrased sentence, use “whom.” "
The only problem is, it's simply not accurate. If we look at language we can easily see that these "rules" as propogated by the offered site do not adequately describe how who/whom are used in modern English.
Clearly, 'who' functions for both subject and object forms.