In this entry we are
going to talk about this grammar topic called Passive voice
Use
of Passive
Passive voice is used when the focus is on the action. It is not
important or not known, however, who or what is performing the action.
Example: My bike was stolen.
In the example above, the focus is on the fact that my bike was stolen.
I do not know, however, who did it.
Sometimes a statement in passive is more polite than active voice, as
the following example shows:
Example: A mistake was made.
In this case, I focus on the fact that a mistake was made, but I do not
blame anyone (e.g. You have made a mistake.).
Structure
Object/ action + to
be + verb in past participle (by + subject)
In the sentence, the
author of the action is not always showed. So you have to decide if it is
important of not.
Example: The direction are explained (by the teacher)
*The parenthesis are not used
Finally, in the next link you can see more information and practices about the topic