A common noun does not have to be capitalized. Common nouns can be concrete or abstract. Concrete nouns are used to name things people can use their senses to see. A pronoun is used in the place of a noun or phrase. Personal pronouns are used to refer to specific nouns.
Relative pronouns introduce dependent clauses.
Interrogative pronouns introduce a question. Reflexive and intensive pronouns deal with the self. The difference between them is that reflexive nouns name the receiver of an action and intensive pronouns emphasize a noun. Demonstrative pronouns show which nouns perform or receive the action. Indefinite pronouns are used to show an unspecific number of nouns.