I’m tired of people mucking up passive voice, so here it is, once and for all:
A passive sentence is one in which the subject receives the action instead of doing it.
Example: The boy was bitten by the dog.
Snooze fest, right? And easy to correct:
The dog bit the boy.
If you are writing a slightly different kind of story: The boy bit the dog.
Easy, right? Passive voice adds extraneous words and weakens a narrative. Do a quick search of your manuscript for the use of “by” (for PCs: CTRL+F to open the search dialogue box and then search for by with one space before it). Try to change your passive sentences to the active voice.
Passive voice makes sense in limited situations. Writing a mystery?
The man was murdered. -- technically a passive sentence, but notice the lack of "by". In a mystery, we wouldn't know who murdered the man.
Some folks tend to say any sentence with a linking verb (forms of be: is, was, were, etc.) is a passive sentence. Not so. I'll address the weakness of linking verbs in the future.