Personal pronouns replace nouns to avoid repetition. Subject pronouns perform the action or are described: "I," "you," "he," "she," "it," "we," and "they." "You" uniquely serves as both singular and plural, with no distinction in form. The third-person singular forms distinguish gender: "he" for masculine, "she" for feminine, and "it" for neuter, as in "it is raining."
Object pronouns receive the action of a verb or follow a preposition: "me," "him," "her," "them," and "us." The pairings follow clear patterns: I/me, he/him, she/her, we/us, and they/them. A useful test is to drop other words: "She and I went" (not "her and I") versus "He called me" (not "he called I"). Reflexive pronouns like "yourself" refer back to the subject for emphasis or to indicate that the subject performs an action on itself, as in "You should be proud of yourself."
Interrogative and relative pronouns introduce questions or relative clauses. "Who" refers to people, "what" asks about a thing or identity, and "which" is used for things or animals, often when offering choices among a defined set. As relative pronouns, they introduce clauses that describe a noun: "the man who called," "the book that I read," or "the car which I bought."