In order to understand how a verb is used in a passive form in Italian, let’s first look at its opposite: how a verb is used in an active form. A verb is in its active form when the subject is doing/performing the action:
Carlo telefona ai suoi genitori = Carla is calling her parents
I miei fratelli abitano in Germania = My brothers live in Germany
Claudio e Lucia parlano di politica = Claudio and Lucia are talking about politics
Paolo beve un caffè = Paolo is drinking a coffee
On the other hand, a verb is in its passive form when the subject is receiving/bearing the action of the verb:
La macchina è guidata da Alberto = The car is driven by Alberto
Un libro è letto dagli studenti = A book is read by the students
La carne è mangiata dal gatto = The meat is eaten by the cat
Un caffè è bevuto da Paolo = A coffee is drunk by Paolo
The basic formula for the passive in Italian is the following:
(DIRECT OBJECT +) AUXILIARY VERB + PAST PARTICIPLE + (DA + SUBJECT)
In Italian, we will see how the passive voice can be constructed with three different auxiliaries (essere, venire, andare) but its meaning will change depending on the auxiliary you use.
Only transitive verbs (verbs that take direct objects) can use the passive voice. Regardless of the auxiliary you use (a form of essere, venire, andare), the past participle must agree in gender and number with the subject in question, e.g.,
I libri saranno pubblicati.
The books will be published.
La borsa è stata ritrovata.
The bag was found.
La frutta va mangiata.
The fruit must be eaten.
When you use the passive voice (versus the active voice) in Italian, the meaning of the sentence does not change but the perspective does change. For example, in the following sentence the emphasis is on la spesa (the food shopping):
La spesa è fatta da Mary = The food shopping is done by Mary.
The passive voice is also very important in Italian because it is used in written/journalistic Italian very often.