Here's a breakdown:
* Verbs describe actions, states of being, or occurrences. Examples: run, jump, think, exist, happen.
* Nouns are words that name people, places, things, or ideas. Examples: dog, school, book, happiness.
* Pronouns are words that replace nouns. Examples: he, she, it, they, we, you, I.
While some verbs can be used as nouns (e.g., "running" in "Running is good exercise."), they are still fundamentally different parts of speech.