A pronoun is a word used in place of a noun. Using the following paragraphs we try to understand the necessity of pronouns.
Paragraph without using Pronouns
Roshni is a good girl. Roshni is gentle. Roshni is well mannered. Roshni respects her parents and teachers. Roshni is honest and truthful. Roshni is intelligent too.
The same paragraph has been rewritten using Pronoun:
Roshni is a good girl. She is gentle. She is well mannered. She respects her parents and teachers. She is honest and truthful. She is intelligent too.