PASSIVE VOICE

Definition: The passive voice in German is formed by combining the verb "werden" with the past participle of the verb you are making passive in its various tenses. the passive voice is used primarily to describe situations where the activity or process is emphasized.
If mentioned at all, the prepositions used to indicate the agent of the action are:

von : used when the agent is a person or a thing.

durch : used to indicate the means by which the action has been done.

mit : used to indicate the instrument used to perform the action.

Examples in German:

The book is (being) written by me.
Das Buch wird von mir geschrieben.
The book was written by me.
Das Buch wurde von mir geschrieben.
The book has been written by me.
Das Buch ist von mir geschrieben worden.
The book had been written by me.
Das Buch war von mir geschrieben worden.
The book will be written by me.
Das Buch wird von mir geschrieben werden.
The book will have been written by me.
Das Buch wird von mir geschrieben worden sein.

Note: that werden uses a special past-participle (worden) when it is used in the present perfect, the past perfect and the future perfect of the passive voice.

Examples in Active and Pasive:

Active:
One doesn't smoke here.
Hier raucht man nicht.

Passive:
There's no smoking here.
Hier wird nicht geraucht.

Note: In German, the passive voice can appear without any subject of the verb, or with an impersonal subject es.

No parking here.
Hier wird nicht geparkt.

No smoking in the corridor.
Im Gang wird nicht geraucht.

There was lots of dancing and singing.
Es wurde viel getanzt und gesungen.