Person is how you know whether a given pronoun is referring to the speaker, the one spoken to, or the one spoken of.
- first person is used when referring to the speaker (I, me, we, us);
- second person is used when referring to the one spoken to (you, your); and
- third person is used when referring to the one spoken of (he, she, it, they, them, any noun, etc.).
cf. personal pronouns, video