This is the 1677th most frequent Russian word.
татарстана
"Tатарстана" translates to "of Tatarstan," indicating possession or relation to Tatarstan, a region in Russia.
Here, 'Татарстана' is used in its prepositional case (Татарстане) because it follows the preposition 'в', indicating location.
Я был в Татарстане летом.
I was in Tatarstan in the summer.
Here, 'Татарстана' is in the genitive case, showing possession ('capital of Tatarstan').
Столица Татарстана - Казань.
The capital of Tatarstan is Kazan.
Again, 'Татарстана' is in the genitive case to indicate the culture belonging to Tatarstan.