This document discusses different types of relative clauses, including defining and non-defining clauses. Defining clauses provide essential information to the meaning of the sentence, while non-defining clauses provide extra contextual information. The document also covers the different "linkers" or relative pronouns used to introduce relative clauses like who, which, that. It provides examples of defining and non-defining clauses and discusses when the relative pronoun can be omitted. Adverbial relative clauses introduced by words like when, where, why are also briefly covered.