learn the Italian language with Italian culture

Definite article: ‘the’
The first thing to know is that the Italian language uses definite articles a lot more than in English when speaking generally. For example, where we would say beautiful women, Italians would say le belle donne (the beautiful women) or il cibo italiano instead of italian food

Next we should remember that articles have to agree with their nouns, taking into account whether they are masculine, feminine, singular or plural:

Masculine singular - il - eg ‘il libro‘ (the book)
(nouns starting with particular combinations of letters - lo - eg lo squalo (the shark)

Masculine plural - i - eg ‘i libri‘ (the books)
(nouns starting with particular combinations of letters - gli - eg gli squali (the sharks)

Feminine singular - la - eg ‘la penna‘ (the pen)

Feminine plural - le - eg ‘le penne‘ (the pens)

Indefinite articles: ‘a/an/some’
As before, indefinite articles have to agree with their nouns.

Masculine singular - un - eg ‘un libro‘ (a book)
(nouns starting with particular combinations of letters - uno - eg uno squalo (a shark)

Masculine plural - dei - eg ‘dei libri‘ (some books)
(nouns starting with particular combinations of letters - degli - eg degli squali (some sharks)

Feminine singular - una - eg ‘una penna‘ (a pen)
Feminine plural - delle - eg ‘delle penne‘ (some pens)

Masculine nouns which start with the following combination of letters use lo/gli or uno/degli:
sb, sc, sd etc, gn, ps, x, y, z