This is the 74th most frequent Polish word.
polska
Polska: Poland (a country in Central Europe).
This is an example of 'Polska' as a proper noun, representing the name of the country Poland.
Polska leży w Europie Środkowej.
Poland is located in Central Europe.
In this sentence, 'Polskę' is the accusative case form of 'Polska', used as a proper noun signifying the country.
Poznałem Polskę podczas mojej podróży.
I got to know Poland during my journey.
Here, 'polską' is an adjective in its accusative feminine singular form, derived from 'Polska', describing the word 'kulturę' (culture).