Who are the Uighurs?

http://youtu.be/ri3zlO6q03M Over a year ago there were riots and fighting between the Uighurs and the Han Chinese in Urumqi, the capital of Xinjiang province. Today there is calm in the city. The Chinese government blamed overseas Uighurs for instigating the unrest. We saw unlimited prosperity for the Han immigrants in the area, there is lots of trading with Central Asia. I went to a money changer to convert some US$600 into Chinese Yuan, there was a Uighur man who had a few thousand US dollars to convert to Yuan, made me embarassed over my paltry sum of US dollars.