Essere means "to be" and changes its ending for each person: io sono, tu sei, lui/lei è, noi siamo, voi siete, loro sono. Because the verb ending already tells you who you are talking about, Italian normally leaves out the subject pronoun (io, tu...) unless you want to stress it.
Examples
- Sono Marco, e tu?
- I'm Marco, and you?
- Lei è di Roma.
- She is from Rome.
- Siamo italiani.
- We are Italian.
The mistake to avoid
Saying "Io sono Marco" every time sounds heavy — drop io unless you are contrasting yourself with someone else.
Where this fits in
Greetings & introductions, Italian A1: Say hello, give your name, ask someone else's, and where they're from.