This is the 6635th most frequent Russian word.
latvijas
"Latvijas" is not a Russian word; it is Latvian and means "of Latvia" or "Latvia's" (possessive form).
Here, 'латвийскую' (Latvian) is used as an adjective derived from 'Латвия' (Latvia) to describe 'музыку' (music), referring to music from Latvia.
Я люблю латвийскую музыку.
I love Latvian music.
In this sentence, the word 'Латвии' is the genitive form of 'Латвия', meaning 'of Latvia', indicating origin.
Мой друг из Латвии.
My friend is from Latvia.
'Латвии' again in the genitive form here specifies ownership or association with the flag.