Here's why:
* Nation: Refers to a group of people who share a common identity based on culture, history, language, and often, a shared territory.
* State: Refers to a political entity with a defined territory, government, and sovereignty.
A nation-state is a political entity where the nation and the state coincide. This means that the people who identify as a nation also occupy the same territory and are governed by the same state.
While not every country perfectly embodies this ideal, many countries strive to be nation-states, and the concept is deeply embedded in modern political thought.