The passive voice is used when we want to emphasize the action (the verb) and the object of a sentence rather than the subject.
This means that the subject is either less important than the action itself or that we don’t know who or what the subject is.
Passive: My scooter was stolen.
Active: Someone stole my scooter
Passive: Chianti area is known for its excellent wines.
Active: Many people know Chianti area for its excellent wines.
Passive: Twenty people were injured in the terror attack.
Active: Someone injured twenty people in the terror attack.
The passive agent
When we know who the accomplish the action and we put it/ him her/them at the end with by.
We call this an agent.
Passive: The "Mona Lisa" was painted by Leonardo Da Vinci
Active: Leonardo Da Vinci painted the Mona Lisa.
Headlines (both newspaper headlines and TV / radio headlines) tend to use passive voice structures.
Why?
Because that way:
a. you can make the relevant information the focus of information, by placing it at the beginning of the sentence:
A Lidl employee is believed to have been fired for working too much.
Paul McCartney is considered the “most successful songwriter in history”.
b. you can be more impersonal in your statements:
It is estimated/ believed that cybercrime costs the global economy $445 billion a year.
Cybercrime is estimated to cost the global economy $445 billion a year.