MASCHILE E FEMMINILE  (Masculine and Feminine)

In Italian, NOUNS are either Masculine of Feminine. 

Typically, nouns ending with -O are masculine, while nouns ending with -A are feminine.

BAMBINO ("male child" ) is a MASCULINE noun
BAMBINA ("female child") is a FEMININE noun

ARTICLES and ADJECTIVES must agree in gender (masculine or feminine) with the NOUN they are associated with.

 UN BAMBINO ITALIANO 

UN  ("a") is the masculine form of the indefinite article
UNA ("a") is the feminine form of the indefinite article

ITALIANO / ITALIANA are respectively the masculine and the feminine form of the adjective.