What best describes the three parts of a pronoun?

Pronouns don't actually have "three parts". You're likely thinking of the three cases of pronouns:

* Nominative: This is the case for pronouns used as the subject of a sentence. Examples: I, you, he, she, it, we, they.

* Objective: This is the case for pronouns used as the object of a verb or preposition. Examples: me, you, him, her, it, us, them.

* Possessive: This is the case for pronouns that show ownership or possession. Examples: my, mine, your, yours, his, hers, its, our, ours, their, theirs.

Let me know if you have any other questions!