Si impersonale
The si impersonale is roughly the English equivalent of “one, you, we or they” as in “you can’t smoke here” = Qui non si fuma.
It is used to describe what people (in general) do or don’t do. E.g.,
Si vive bene in Italia.
You live well in Italy.
Forms of the si impersonale:
A. It is formed with the impersonal pronoun si, followed by the 3rd person singular form of the appropriate verb. E.g.,
Si va lentamente in quel corso.
(We) go slowly in that course.
Si mangia bene in quella trattoria.
One eats well in that restaurant.
In questo locale si gioca a carte, si mangia, si canta e si balla tutti insieme.
In this place you play cards, you eat, you sing, you dance—all at this one place.
The si impersonale is used with intransitive verbs (viaggiare, giocare, andare, etc.) or with transitive verbs that do not have a direct object (look at the examples above with si mangia and si canta, take note of how they are used without a direct object).
B. The following rule does not have an equivalent in English, so you have to follow the logic of the Italian syntax: Adjectives and nouns referring to the si impersonale as a subject must use the masculine plural ending.
Quando si è felici, tutto va bene.
When you’re happy, everything goes well.
Quando si è genitori, bisogna essere comprensivi.
When you become a parent, it is important to be understanding.