This is the 324th most frequent Italian word.
stati
"Stati" in Italian means "states" (plural of "state") or "been" (past participle of "essere" in certain contexts).
In this sentence, 'stati' functions as a past participle auxiliary in the passive voice, indicating an action performed by an implied agent.
I libri sono stati posizionati sul tavolo.
The books have been placed on the table.
Here, 'stati' refers to the auxiliary verb in the passive form, expressing an occurrence in the past.
In passato, sono stati molti a dedicarsi a questa arte.
In the past, many devoted themselves to this art.
In this context, 'Stati' is part of a proper noun 'Stati Uniti', meaning 'United States,' and refers to the union of states as a geographical and political entity.