The document is a discussion in Spanish between Sergio, Paola, and Susan about the past perfect tense in English. It begins with Sergio confirming that the past perfect tense is used to talk about an action that occurred before something else in the past. Paola notes that it is equivalent to the past pluperfect tense in Spanish. They then discuss how to form the past perfect tense in English, including using the auxiliary verb "had" plus the past participle, and providing examples of its use.