This is the 2413th most frequent Japanese word.
ベトナム
Vietnam.
In this sentence, ベトナム is used as a proper noun representing the country Vietnam.
ベトナムは美しい国です。
Vietnam is a beautiful country.
Here, ベトナム modifies the word 料理 to describe the cuisine of Vietnam.
私はベトナム料理が好きです。
I like Vietnamese cuisine.
In this context, ベトナム serves as a proper noun indicating the physical location, Vietnam.