What is the passive?

The passive is used in sentences for which the agent (person doing the action) is irrelevant or unknown. For example 'the door was opened' would use the passive voice and be translated as 'der Tür wurde geöffnet'. In this sentence, the object is the subject. I.e. the door is the thing on which the action is being carried out. The passive can also be used in sentences where the agent is determined. For example 'the door was opened by the man' would be 'Der Tür wurde von dem Mann geöffnet'