Pronouns are words that take the place of a noun. Pronouns are used instead of a noun. If we didn't have pronouns, we would have to repeat a lot of nouns! So pronouns are used in place of nouns to avoid repetition.
Example
Personal Pronouns: Personal Pronouns are used are substitutes for proper or common nouns.
Possessive Pronouns
Interrogative Pronouns: These pronouns are used to introduce questions.
Demonstrative Pronouns: Demonstrative Pronouns are used to point out objects.
Indefinite Pronouns: Pronouns which refer to things in a general way and not to someone or something in particular.
Reflexive Pronouns: This class of pronouns is used when the object is same as the subject of the sentence.