The document discusses the passive voice and how it compares to the active voice. It explains that in the passive voice, the subject of the active sentence becomes the agent in the passive sentence, and the direct object of the active sentence becomes the subject of the passive sentence. This change is made by using the appropriate form of "to be" plus the past participle of the main verb. The same transformation is demonstrated across different verb tenses, including present, past, future, and perfect. Examples are provided to illustrate how sentences are changed from active to passive voice while maintaining the same meaning.