Passive voice is a grammatical construction where the subject of the sentence receives the action rather than performing it. In this structure, the focus is on the action itself or the recipient of the action, often using a form of the verb "to be" followed by the past participle of the main verb. For example, in the sentence "The book was read by John," the emphasis is on the book rather than on John. In contrast to active voice, where the subject performs the action (e.g., "John read the book"), passive voice can make sentences less direct. It is often used in formal writing or when the doer of the action is unknown or irrelevant. Understanding passive voice helps improve clarity and variety in writing.