Paul W. answered 10/23/19
Dedicated to Achieving Student Success in History, Government, Culture
As you can see, the term 'Nation State' is actually two terms, 'Nation' and 'States.' The original meaning of the term 'Nation' was, in essence, a people with a common culture, such as one specific shared language.
The term 'State' refers to a specific government or political system that exercises the exclusive authority to rule a specific territory.
A 'Nation State', therefore, combines the features of these two terms. It is a people who share in common both a specific, sovereign government that has the exclusive power to rule over them and, to one degree or another, some form of shared culture.
As such, although the term 'Nation State' is commonly used as a label for specific countries (example: the Nation State of Argentina), this term has more to do with an ideal envisioned by some Europeans in the 19th and first half of the 20th century. The birth of modern Germany in 1871, for instance, achieved by the unification of a number of big and little German kingdoms, was preceded by calls by various German speaking individuals for a 'State' that would incorporate the German 'Nation' (in other words, the German 'People', people who shared a common 'German' culture).
Today, countries are less likely to be depicted exclusively based on the dominant culture. The United States, for instance, is not viewed exclusively as a Caucasian, Protestant, English speaking country. While the people of the United States are ruled by a single, specific central government (the Federal Government), they do not all necessarily share a common culture.
And, for that matter, neither did, for instance, modern Germany at the time of its creation in 1871 or today. In 1871, for instance, while the majority of people may have shared a common 'German' culture, such as speaking the German language, the newly created 'Nation State' of Germany also contained many non-German peoples, such as Danish speakers, Poles, Jews, etc... In this respect, the term 'Nation State' technically refers to an ideal that has never actually been realized.