I, you, he, she, we, they. These are what grammarians call the subject pronouns—they stand in for the subject: "she" instead of "Teresa," or "they" instead of "the children." Observe the following examples in Italian:
Noi non facciamo così! (We don't do it like that.)
Domani io faro un esame. (Tomorrow I'm taking an exam.)
Voi studiate per l'esame? (Are you studying for the exam?)
Domani vieni a lezione tu? (Tomorrow are you going to the lesson?)
Oftentimes, the subject pronouns are implied in Italian since the form of the verb already indicates the number, gender, and case of the subject. The same sentences in the previous list have the same meaning even with the subject pronouns omitted. To review the subject pronouns, see the table below.
ITALIAN SUBJECT PRONOUNS
PERSON
SINGULAR
PLURAL
I
io (I)
noi (we)
II
tu (you, informal)
voi (you)
III
lui, lei (he, she)
loro (they)
Lui (you, formal)
Loro (you, formal)
There are a few cases in which subject pronouns are required in Italian.
For contrast: Noi lavoriamo e tu ti diverti. (We work and you amuse yourself.)
For emphasis: Lo pago io. (I'll pay for it.)
After the words almeno, anche, magari, neanche, nemmeno, neppure: Neanche noi andiamo al cinema. (We aren't going to the cinema either.)
When the subject pronoun stands by itself: Chi voule giocare? Io! (Who wants to play? I do!)
From:https://www.dbfei.com/Article/yidaliyu/201311/7671.html