1. Instead of using the same word again and again, a pronoun is used.
2. For example: Rita bought a dog. She named it Charlie.
'She' is used instead of the name 'Rita' and 'it' is used instead of the 'dog'.
1. A noun is a part of speech which is used to identify names, people, places, things etc.
2. For example: Rita bought a dog.
Here, 'Rita' and the 'dog' are nouns.
HOPE I HELPED :)