Active Voice: Subject + verb + object
In a sentence with an active voice, the subject of it is the agent/doer of action while the object of the sentence is the receiver of the action.
"My school's principal instituted a new school policy." ---> The subject of action is the school principal.
"Russia is the largest country in the world."
Passive voice: Subject + to be + past participle
In a sentence with a passive voice, the subject of the sentence is the receiver of action. There is usually no mention of an agent.
"A new school policy was instituted by them." ---> "By them" makes it passive.
"It was a hard time."
