Look at this example of a passive sentence in English:
The computers were sold by the shop assistant.
- the computers = the object acted on by the verb
- by the shop assistant = the person performing the action
We use the Voz pasiva in these cases:
1. When we give more importance to the action than to the subject. In these cases the subject is not normally mentioned. For example:
2. If we want to emphasise the subject of the action using generally por + [agent]. For example:
- The conjugated verb in the passive voice is "ser" and can be conjugated in any tense.
- The participle always agrees with the subject of the passive sentence in gender and number!
See also Voz pasiva