This document provides an overview of relative clauses in English. It discusses defining and non-defining relative clauses. Defining relative clauses identify or define the antecedent noun, while non-defining clauses provide additional information about the antecedent. The document outlines the different types of relative pronouns used for people and things based on their role in the clause. It also discusses the placement of prepositions and omitting pronouns in some cases. Examples are provided to illustrate the key differences between defining and non-defining relative clauses.