Who were the Celts?  As per Celtic Fashions Website.

The Celts were an ancient Indo-Ejuropean people whose culture developed in the are of the Black Sea 6-8000 years ago.  They migrated throughout Western Asia and Europe arriving in the British Isles around 600 BCE.  The Celts of Britain and Gaul were a warlike people resisting Roman conquest i the first century BCE.  Only Ireland and Northern Scotland escaped conquest.  After the Romans other invasions took place.  Christian Missionaires were successful in converting the Celts of Ireland and Scotland, Saxons, Vikings and Normans invaded and were met with fierce resistance by freedom fighters like Arthur.  Today four Celtic languages in six Celtic Nations (Ireland, Scotland, Wales, Cornwall, Isle of Man, Brittany) have survivied.