A pronoun replaces a noun to avoid monotonous repetition. The noun that a pronoun replaces is called its antecedent. For grammatically sound sentences, a pronoun must agree with its antecedent in number, person, and gender.
Subject vs. Object Pronoun Case
Use subject pronouns (I, he, she, we, they) when performing the action. Use object pronouns (me, him, her, us, them) when receiving the action or following a preposition.
Incorrect: Between you and I, this secret is safe.
Correct: Between you and me, this secret is safe. (After preposition 'between')
The 231 Order of Pronouns
When good deeds or normal actions involve multiple personal pronouns, follow the 231 order: Second person (You), Third person (He/She), First person (I).
Correct: You, he, and I will attend the seminar together.