In China's "Autonomous Regions", a separate political division from provinces, a minority ethnic group has been designated apart from the Han Chinese. While still ruled from the central government, these regions are supposed to have more legislative authority and the ability to appoint a governor from their own ethnicity.
Practically speaking, you wouldn't walk into a booking office and say "I want to go visit an AR". People refer to these areas by their mandarin names.
There are five Autonomous Regions in China. Listed alphabetically by their names in mandarin below, click through for more information.