In understanding passive voice, it would be best to show what active voice is first.
When using active voice, the subject in a sentence is the one performing the action with an object or another person. Active voice makes what you are writing and communicating clearer, and concise in what you want to say.
Examples of active voice sentences:
Grandma is baking a cherry pie.
Karl Benz, created the first car.
He was sculpting a stone statue.
Mario is searching for the Princess.
Example of active voice in fiction:
Heart of Darkness (by Colin Higgins)
The Great Gatsby (F. Scott Fitzgerald)
In writing passive voice, you still have an action that is happing, the difference is that that instead, the subject is the recipient of the action. Passive voice is not wrong, it is that active voice is more direct and clearer for the reader.
Let us look at the previous examples, except this time, the object will be the focus.
A cherry pie is being baked by grandma.
The first car was created by Karl Benz.
A stone statue was being sculpted by him.
The Princess is being searched for by Mario.