Verbs are either active or passive in voice.
In the active voice, the subject and verb relationship is straightforward: the subject is a do-er.
In the passive voice, the subject of the sentence is not a do-er. It is shown with by + do-er or is not shown in the sentence. Passive voice is used when the action is the focus, not the subject. It is not important (or not known) who does the action.
Example:
Passive voice should be avoided when you want more clarity in writing. However, in some cases, you need to use passive voice to stress the action, not the actor. Also, passive voice can be considered more polite, as it sounds less aggressive or dramatic.
You can easily rewrite an active sentence to a passive sentence. The object in the active sentence becomes a subject in the passive sentence. The verb is changed to a “be” verb + past participle. The subject of the active sentence follows by or is omitted.