The four basic requirements for a nation-state are sovereignty, population, territory and government. In other words, nation-states must rule themselves, have a system of rule, people and a place to rule over.
Examples of nation-states include Brazil, Russia, Australia, Mexico, Paraguay, Vietnam and Greece. A nation is simply a cultural tie between large groups of people. A state is the political entity that they have organized. One province in Canada, Quebec, uniquely speaks French-Canadian. This cultural thread makes the citizens of Quebec a nation within a larger nation-state of Canada, as Quebec does not have its own sovereignty.