Yugo (or better Zastava Koral) is a car manufacturer based in Kragujevac, Serbia. I assume it derives its name from the country that was Yugoslavia. Its models were license built Fiat cars.
Yugo as a brand of cars is (geographically) not very widespread even though several attempts were made to even penetrate the American market. However, hundreds of thousands Yugos were built over the year of which over 140k were exported to the US.
Any Yugo on the Ambulance Photos site are subcompact based vehicles, for example ambulance cars.