Other forms: endonyms
An endonym is a place name that's used by the people who actually live there. If you're planning a trip to Spain, you probably know that the country's endonym is España.
With the thousands of spoken languages in the world, and hundreds of written ones, it shouldn't be surprising that many places have been given names that are easier for non-natives to pronounce or spell. That's how the city of Wien in the country of Österreich became Vienna, Austria. In this case, Wien is an endonym (the name used by Austrians) and Vienna is an English exonym. Endonym is from Greek roots meaning "inside" and "name."