This is the 2009th most frequent German word.
italienische
"Italienische" means "Italian" (adjective).
In this sentence, 'italienische' is used as an adjective modifying the noun 'Pizza' to indicate its origin or style.
Ich liebe italienische Pizza.
I love Italian pizza.
Here, 'italienische' again is an adjective describing 'Kunst' to specify the category or origin as Italian.
Italienische Kunst ist weltweit bekannt.
Italian art is globally famous.
In this example, 'italienischen' is the adjective form adjusting for the masculine noun 'Sonnenuntergang' and its accusative case.