What's the difference between object and subject?

[X-III]

because in WHo or WHom Test, there are two similar questions:
1. Who is often used as a relative pronoun when it is the object of a verb.
2. Who is often used as a relative pronoun when it is the subject of a verb.

the answer to both is true, but what are the difference?

oh , and plz, did i say it right? "the answer to both are true" or "the answer to both is true"? thanx!

[endeavor6636]

subject is the "main object" in a sentence
obeject is the "second object" in a sentence



EX : a man was kill by the dog. ( the man is the main obeject you are taking about - "subject" . the dog is the second object -"obeject")

ex: the house was built in 1993
a man built a house yesterday