In a sentence, the action happens to the object. It might be a direct object, an indirect object, or the object of a preposition, but action always happens to an object.
These are the object pronouns: me, you, him, her, them, us, it
It happens to me. It happens to you.
It happens to him. It happens to her.
It happens to them. It happens to us.
It happens to it.
A direct object directly receives action from the subject. Look at these sentences with a direct object:
Mary caught the football. Then Mary threw it to Janet.
Football is a direct object. Mary caught what? Mary caught the football.
In the next sentence, it is a direct object. Mary threw what? Mary threw it.
Because we used football in the first sentence, we know it is the football.
Football is an antecedent. The pronoun it replaces the noun football.
The object of a preposition is at the end of a prepositional phrase. Look at these sentences with prepositional phrases:
Don bought a necklace for Sarah. Don gave the necklace to her last night.
The prepositional phrase in each sentence is underlined.
Sarah is the object of the preposition in the prepositional phrase for Sarah.
In the next sentence, her is the object of the preposition in the prepositional phrase to her.
Because we used Sarah in the first sentence, we know that her replaces Sarah in the second sentence.
Sarah is the antecedent, and her is the pronoun that replaces Sarah.
Let’s use the same sentence to talk about a pronoun as an indirect object.
Don bought a necklace for Sarah.
We can take away the prepositional phrase and make Sarah an indirect object, like this:
Don bought Sarah a necklace.
Sarah is still the antecedent. We use her for the pronoun replacing the antecedent. The sentence looks like this:
Dan gave her the necklace last night.
We know that her refers to Sarah because Sarah was mentioned in the first sentence.
Object pronouns can take the place of nouns acting as a direct object, an indirect object, and the object of a preposition. Just remember to always use an antecedent noun before using a pronoun.