The passive is a grammar construction that uses the auxiliary to be and the past participle of a verb:

• My camera has been stolen.
• The Mona Lisa was painted in 1503.
• We are being followed.
• She was seriously injured in the car crash.
• You will be told when to come.
• The school was built just after the war.
• The ski race has been cancelled due to lack of snow.

We use the passive when we are more interested in what happened than who did it. For example, in saying My camera has been stolen the speaker is conveying important information about his camera. The camera is the focus of interest, and so the speaker has made it the subject of the sentence. He does not know or care who took it. Similarly, in the sentence The Mona Lisa was painted in 1503 the speaker wants to tells us when the painting was done. She is not interested in telling us who painted it, or maybe she expects us to already know that it was painted by Leonardo da Vinci.

The passive can be used in all tenses. The following list has examples of the most common uses:

• The classrooms are cleaned every afternoon. (present simple)
• A new road is being built behind the school. (present continuous)
• The boy was seen spraying paint on the wall. (past simple)
• I was late because the road was being repaired. (past continuous)
• The car thief has been caught. (present perfect)
• The painting had been damaged during the war. (past perfect)
• You will be shown how to do it. (future)
• It must be done. (modal verb + simple infinitive)
• She likes to be praised when she does well. (infinitive with to)
• I hate being watched when I'm working. (gerund)

Note: In all the above sentences, it is not important to the speaker that s/he tells us who (e.g., who cleans the classrooms, who is building the road behind the school, who saw the boy spraying paint). Important is: what (or when, why, how).

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