FormTo be + past participle
Tense
Present simple, past simple, present perfect and future.
is/are was have/has will
When do we use it?
1. When who did the action is not known, or is not important.
-use 'by' at the end of the passive sentence if you want to include who did the action.
The phone was invented in 1875.
The phone was invented in 1875 by Alexander Bell.
2. Remove focus of subject, like avoiding blame.
Sara did not hand in our group assignment.
Our group assignment was not handed in.