Possessive pronouns, such as "mine," "yours," "hers," "his," "theirs," and "ours," are used to show ownership or possession of a noun. They replace the noun and demonstrate who owns or possesses it. For example, instead of saying "The car of John," you can say "John's car." Possessive pronouns can also be used to indicate a relationship between two nouns, such as "her father's house" or "their company's profits."