English and ESL Instructor
Active: William Golding wrote Lord of the Flies.
Passive: Lord of the Flies was written by William Golding.
The meaning of the two sentences above are exactly the same, but the difference is in the format of the sentence. In the active construction, the sentence follows the conventional subject-verb-object format. In the passive construction, the sentence begins with the object, followed by was/were, the past participle, and then the subject.
In come cases, there is no identifiable subject in the passive voice:
My house was broken into. (In this case, the subject is not known.)
In formal writing assignments, it is best to avoid using the passive voice if at all possible. Even in the example above, where the subject is unknown, we can still say, Somebody broke into my office.