What is the passive voice and when do you use it in Spanish?

It is helpful to understand the passive voice in the context of its counterpart, the active voice. We see the difference between active and passive in these sentences:"The girl wrote an email.""An email was written." In the former sentence, the girl is the subject because she is the one doing something. In the latter, the email is the subject.In Spanish, there are two ways of expressing the passive. The first uses 'se' and the conjugated verb. "Una chica escribió un correo" becomes "Se escribió un correo".The second uses the preterite conjugation of 'ser' and the past participle. "Una chica escribió un correo" becomes "Un correo fue escrito" (the past participle in this instance is irregular). This is a more literal translation of the English.For this second method, the past participle must agree with the subject. If it were a letter ('una carta') instead of an email, it would become "Una carta fue escrita" because the 'carta' is feminine.