Object receives it.

Joe read a book.

sub=Joe

verb=read

object=book

The dog ate the bone.

sub=dog

verb=ate

object=bone

I changed the tire.

sub=I

verb=changed

object=tire

An object is a noun that is the recipient of the verb in the sentence. It’s easier to demonstrate than to explain:

Xena grabbed her sword.

Xena is the subject, because she performs the verb. “Grabbed” is the verb; “her” is a possessive pronoun; the sword is the direct object because the grabbing is performed upon it.

http://www.englishchick.com/grammar/grrem.htm#doio

He ate a banana

In the above sentence some action has been done.

It was done by ‘he’. so he is the subject of that sentence.

What was the action done by ‘he'(subject)

the answer is ‘ate’

‘which one did he eat?’

the answer is a ‘banana’

It is the object of the verb ‘eat’ in this sentence.

“The receiverer or the sufferer of the action done by the subject is called the object.’

You can find it by asking a question by Putting ‘Which’ before the verb.

There’s a verb: action

There’s an object: what the action did to _____ (that’s the “object,” [person, place or thing], of most phrases.)

Example: Mary (noun) wrote (verb) letters. (object)

An object is also described as the thing that is the focus of the action. In this case, it is “letters.” “…letters” is the focus (object) of the verb “wrote…” See? A little?

Helpful? Yay.