Passive voice is a grammatical construction in which the subject of a sentence is acted upon by the verb, rather than performing the action themselves. In passive voice, the focus is on the action being done rather than the doer of the action. This can be achieved by using a form of the verb "to be" followed by the past participle of the main verb. Passive voice is often used when the focus is on the result or the action itself, rather than the person or thing performing the action. It is also commonly used in formal or academic writing.