This is the 3961st most frequent Polish word.
tarnów
Tarnów: A city in southeastern Poland.
Here 'Tarnów' is used as a proper noun referring to the city of Tarnów.
Tarnów jest pięknym miastem w Polsce.
Tarnów is a beautiful city in Poland.
In this sentence, 'Tarnowie' is the locative form of 'Tarnów', indicating location.
Czy byłeś kiedyś w Tarnowie?
Have you ever been to Tarnów?
Here 'do Tarnowa' shows the direction or destination, meaning 'to Tarnów'.