The document discusses relative pronouns in Spanish. It defines a relative pronoun as a proposition that is essential for clearly understanding the antecedent, or reference, in the sentence. The example given is "The man who told me this refused to give me his name," where "who told me this" is the relative pronoun that clarifies which man is being discussed. Relative pronouns should not be separated from the antecedent by a comma. The document then covers appropriate use of relative pronouns like "who," "whom," "whose," and "which" for people and things in different grammatical roles.