The noun defines a person place or thing. A pronoun is something you can use instead of a noun. Hence, if you something to substitute a noun you can easily use a pronoun. The English language is complex and has certain rules.
Each sentence has a subject which is the noun or the pronoun and also has a function which is a verb. The pronoun can be used to replace a noun. It can also be used to replace another pronoun so it can replace anything. It is a strong word and is also used to portray a person place or thing.
In the English language the parts of speech make up the structure of a sentence. A sentence must have a subject and an action. Nouns serve as subjects and verbs serve as actions. Pronouns are a specialized group that can replace a noun or another pronoun.
Some examples of pronouns are: I, me, her, him, mine, she, him, us, and we. These words can be used in places where nouns would be otherwise used. For example if you have already named a person as a proper noun but you want to say something else about them directly after you might use a pronoun such as ‘he’ or ‘she’ instead of restating their name.