They built [this house] in 1486. (active)
This house was built in 1486. (passive)
Channel Islanders speak [French] and English, (active)
[French] is spoken in France, Belgium, Switzerland, the Channel Islands, . . . (passive)
A friend of ours is repairing [the roof].(active)
[The roof] is being repaired by a friend of ours, (passive)
This book will change [your life]
[Your life] will be changed by this book.
When we say what people or things do, we use active verbs. (For example built, speak, is repairing, will change.)
When we say what happens to people or things — what is done to them
— we use passive verbs. (For example was built, is spoken, is being repaired, will be changed.)
The object of an active verb corresponds to the subject of a passive verb.
ACTIVE:
PASSIVE:

Active or passive?
We often prefer to begin a sentence with something that is already known, and to put the 'news' at the end. Compare:
Your little boy broke my kitchen window this morning.
That window was broken by your little boy.
In the first sentence, the hearer does not know about the broken window. So the speaker starts with the little boy, and puts the 'news' — the window — at the end. In the second sentence, the hearer knows about the window, but does not know who broke it. By using a passive structure, we can again put the 'news' at the end.
Another example:
'John's writing a play. ' I didn't know that.'
'This play was written by Marlowe. ' 'Was it? I didn't know that. '

To make passive verb forms, we use the auxiliary be. .

Terminology
Terminology :
aetiology : the science of causation.      .. More >>