Remember that tu and its plural form voi are used in addressing members of the family, peers, children, close friends, and animals. In all other cases, Lei and its plural Loro are used. Note that Lei and Loro always take, respectively, the third person singular and the third person plural of the verb.
Ascolti, Luisa? (Are you listening, Luisa?)
Ascoltate, ragazzi? (Are you listening, boys?)
Ascolta Lei, signorina Rossi? (Are you listening, Miss Rossi?)
Ascoltano Loro signorine? (Are you listening, young ladies?)
Singolare
Singular
io
I
tu
you (familiar)
lui (egli/esso)
he
lei (ella/essa)
she
Lei
you (formal)
Plurale
Plural
noi
we
voi
you (familiar)
loro (essi)
they (m.)
loro (esse)
they (f.)
Loro
you (formal)
Since the endings of conjugated verb forms indicate person and number, subject pronouns may be omitted in Italian except when necessary: (1) for clarity, (2) when modified by anche (also), or (3) when emphasis or contrast is desired. It and they referring to things are almost never used in Italian and need not be translated.