This is the 99th most frequent Russian word.
россия
"Россия" means "Russia," the largest country in the world, located in Eastern Europe and Northern Asia.
The word "Россия" refers to the proper noun name of the country Russia.
Россия - огромная страна.
Russia is a vast country.
Here, "Россию" is the accusative case form of the word "Россия," showing movement toward the country.
Я мечтаю поехать в Россию.
I dream of traveling to Russia.
In this usage, "России" is the prepositional case form of "Россия," used to indicate location within or related to Russia.