The passive voice is used to emphasize the recipient of an action rather than the performer. It is formed using a form of the verb "to be" plus the past participle of the main verb. Examples of the passive voice include "the house was built in 2016" and "was the house built in 2016?". The passive voice is used when the recipient/object is more important, the performer is unknown, or to emphasize the circumstance of an action like "the road is being repaired". It typically uses "by" to indicate the performer/agent.