Active and passive voice refer to whether the subject performs or receives the action of the verb. There are two types of voice: active and passive. In active voice, the subject performs the action, while in passive voice the subject receives the action. When changing a sentence from active to passive voice, the object becomes the subject, "by" is added, and the original subject moves after "by". Certain auxiliary verbs like will, shall, can, or may do not change position in the passive form.