What is third person passive voice? I need to know for a paper.

Third person is when the narrator is not an actual character in the story, and refers to the characters by name or by "he," "she," "they," etc.

The passive voice is when the character isn't actually doing anything, and the verbs that describe his actions are forms of the verb "to be": am, is, are, was, were, be, being, been. These verbs could be attributed to a rock as appropriately as they could be attributed to a person.

The third-person passive voice incorporates both of these.

The third-person passive voice is expressed as:
a third-person noun or pronoun subject of the sentence + any tense of the verb "to be" ...
BUT the subject is the Receiver, not the Doer of the Action .

In the Passive Voice, the Agent (Doer of the Action) is either not mentioned, or is introduced by the preposition "by":

He is being told to behave himself. [by whom is not stated]
He is being told to behave himself by his parents. [parents are the agents]

She was not allowed to go to the party.
She was not allowed to go to the party by her mother. [mother is agent]

The contract (It) will be finalized on Wednesday. [don't know by whom]
It will be finalized on Wednesday by the corporate attorney.

The Passive Voice is used when we don't know who did or said something, or maybe it's not necessary to say.

Examples of Active versus Passive Voice:
Active : He told her to be on time.
Passive: She was told to be on time.

Active: We invited them to attend the lecture.
Passive: They were invited to attend the lecture.

Active: He stole an apple from the market.
Passive: An apple was stolen from the market.

Here's something a little different:
Active: They swore to tell the truth before they testified.
Passive: They were sworn in by the court clerk before they testified.