Pronoun is a function word that can be used as a substitute or replacement of a noun in a sentence. It is one of the part of speech.
he, his, she, her, they, them, ... - Personal Pronouns
this, these, that, those - Demonstrative Pronouns
themselves, ourselves, ... - Reflective Pronouns
someone, no one, few , ... - Indefinite Pronouns
whose, what, ... - Interrogative Pronouns
who, which, ... - Relative Pronouns