Here's why:
* Third-person nouns refer to people or things that are not the speaker or the person being spoken to. They include:
* He, she, it, they, him, her, them, his, hers, its, their
* Names of people, places, and things (e.g., John, New York, car)
* First-person nouns refer to the speaker:
* I, me, my, mine, we, us, our, ours
* Second-person nouns refer to the person being spoken to:
* You, your, yours
So, while everyone is a third-person pronoun when used generally, individual people can be first-person ("I") or second-person ("you").