Korean is, surprisingly, used by both North and South Korea as an official language, despite the apparent divide in recent years. It is spoken by over 75 million people as their native language. Despite being used by minorities in China and Russia, it is classified as a language isolate; this means it is a language with no relation to any other languages used in the modern world.
Given that the language is an isolate, it is straightforward to track the history of Korean: Modern Korean descended from Middle Korean, spoken from the 11th to 16th Century, which came from Old Korean, which in turn came from Proto-Koreanic.