Who digunakan untuk menjelaskan subjek/pelaku
Whom digunakan untuk menjelaskan objek/penderita
Is that simple.
Ada kalimat seperti ini.
The trainer is delivering a course material to the participants.
Siapa yg aktif/subjek? The trainer.
Siapa yg pasif/objek? The participants.
Now, reconstruct the sentence.
- They are listening to the trainer, WHO is delivering the course material.
- The participants, WHOM the trainer is delivering the material to, is listening very eagerly.
The people of South Jakarta voted for Anxi and Nohr in the last governor election.
- Anxi and Nohr, WHOM the South Jakarta people elected for governor, are from different parties.
- The Jakarta people WHO elected Anxi and Nohr for governor, are of the southern part of the city.
Hope this give you a clue of how to use WHO or WHOM. At least, this is the very simplest explaination I can give.