Pronouns are words we use in place of a noun to avoid repetition. For instance: Sheila is going to the supermarket because Sheila wants to buy tomato sauce. The noun "Sheila" is repetitive. Hence, we use "she" instead. For example: Sheila is going to the supermarket because she wants to buy tomato sauce.
Other examples of pronouns are:
I (I prefer to watch football than play it.)
They (They are the ones who helped me.)
His (That baseball bat over the corner is his.)
Us ( I can't believe that you did it to us.)
On another hand, nouns are names of places, people, things, etc.
For example:
The bus arrives at exactly 8 am.
Children like to play in the park.
I have never tried eating sushi before.
