Here's why "they" isn't any of the other categories you listed:
* Personal: Yes, "they" is a personal pronoun. It refers to people or things.
* Reflexive: Reflexive pronouns (like myself, yourself, themselves) are used when the subject of a sentence is also the object. "They" is not reflexive.
* Intensive: Intensive pronouns (like myself, yourself, themselves) emphasize the noun or pronoun they refer to. "They" is not intensive.
* Demonstrative: Demonstrative pronouns (like this, that, these, those) point to specific things. "They" is not demonstrative.
* Interrogative: Interrogative pronouns (like who, what, which, whom, whose) are used in questions. "They" is not interrogative.
* Relative: Relative pronouns (like who, whom, whose, which, that) connect clauses in sentences. "They" is not relative.
* Indefinite: Indefinite pronouns (like some, any, everyone, nobody) refer to nonspecific people or things. "They" is not indefinite, though it can be used as a singular indefinite pronoun in certain contexts.
In conclusion, "they" is a personal pronoun, and not any of the other categories you listed.