The document discusses the Spanish past anterior tense, which corresponds to the English "I had done something" construction. It notes that this tense implies an action further in the past than another action. It can replace the preterite or pluperfect tenses but only in formal, literary usage. The document provides an example sentence and explains the tense can only be used in writing when time is clearly referenced. It also covers the formation of the past anterior tense using the preterite form of haber plus the past participle, and notes the irregular verbs match those of the perfect tense.