This document discusses relative clauses and how they are used to provide additional information about nouns. It covers defining and non-defining relative clauses. Defining clauses provide essential information, while non-defining clauses provide extra, non-essential information. Relative pronouns like who, which, that are used to join the two clauses, and the pronoun can sometimes be omitted in defining clauses if it is the object. Exercises are provided to practice forming relative clauses and identifying defining vs non-defining clauses.