The document discusses the passive voice and how it differs from the active voice. In the passive voice, the subject receives the action rather than performs it. The passive voice uses a form of the verb "to be" plus the past participle of the main verb. Modal auxiliaries like "can", "should", and "must" can also be used with the passive voice to indicate possibility, advice, or necessity. For example, "The ball can be kicked by Luke" or "The ball should be kicked by Luke".