The document discusses active and passive voice in grammar. In active voice, the subject performs the action stated by the verb. In passive voice, the subject receives the action of the verb. The active voice is more common and direct, while the passive voice is less usual. Examples are provided to illustrate the differences between active and passive constructions, including formulas using different verb tenses and the addition of modal auxiliaries. Positive, negative, and interrogative forms are also demonstrated for passive voice sentences. An exercise with examples of both active and passive voice sentences is included at the end.