In the active voice, the subject performs the action which is received by the object . In other words, the subject is the doer and the object is the receiver.
Subject + verb + object
Daniel hit Marcus
We use the passive voice to show that an action happened to someone or something.
In the passive voice the object acts like the doer of an action and the subject is acts like the receiver of an action or actions.
In the passive voice we commonly use v3/past participle to conjugate sentences although we can also use verbs such as get in the passive tense without the use of the verb to be.
The doer of the action does not have to be known and in many cases is not known.
If we want the doer of an action to be known in the passive tense we use ” by”
Object + be(past) + v3 + ( by ) Daniel
Marcus was hit by Daniel
More on tenses in the passive voice here