A "pronoun" is a word that stands in for a name, a noun, or a noun phrase in a sentence.
Q: Do you know John.
A: Yes, I have met him.
In the answer, "I" is a pronoun, standing in for my name "MikeNewYork" and "Him" is a pronoun, standing in for "John".
More here: https://www.usingenglish.com/glossary/pronoun.html