In passive voice, the subject of the sentence receives the action expressed by the verb. The emphasis is on the action itself, rather than who or what is performing it.
The structure of a passive voice sentence is typically:
Object of the action
+ Verb past participle
+ Agent optional, preceded by "by"
Passive voice sentences can be useful for shifting the focus to what is being acted upon, concealing the actor, or emphasizing the action itself.
Example:
The mouse
subject
was chased
verb
by the cat
agent