the SUBJECT of a sentence is not the one who acts (or does the action specified
by the verb). In such a case, consider the subject to be PASSIVE; another
person or thing will do the action of the verb.
passive voice, the one who does the action is called the AGENT.
man was bitten by the dog." (passive)
dog bit the man." (active)
Note that in the two sentences above, the event is the same. The difference
in voice is merely who the writer or speaker has chosen to use as the subject
of the action. The choice of voice does not alter the features of the event.