This is the 6923rd most frequent Russian word.
альберто
"Альберто" is a Russian transliteration of the name "Alberto," typically a male given name.
Here, 'Альберто' is a proper noun and functions as the subject of the sentence, referring to a person's name.
Альберто приехал из Италии вчера.
Alberto arrived from Italy yesterday.
In this instance, 'Альберто' is still a proper noun, used to denote the individual to whom the reported thought or action belongs.
Я слышал, что Альберто мечтает посетить Санкт-Петербург.
I heard that Alberto dreams of visiting Saint Petersburg.
'Альберто' here is again a proper noun and is the direct object of the verb 'встретили', indicating the person who is the recipient of the action.