The document discusses the past, present, and future perfect verb tenses in English. It provides examples of sentences using each tense and explains how each tense indicates that an action is completed relative to the specified time frame. The past perfect tense uses "had" plus the past participle verb to refer to something completed in the past. The present perfect uses "have/has" plus the past participle to refer to something completed now. And the future perfect uses "will have" plus the past participle to refer to something completed in the future.