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.
2. Nei Meng Gu (Inner Mongolia)
Capital city: Hohhot
Population: 23.8 million
Designated ethnic minority: Mongolian
Famous for: great grasslands and Mongolian horsemanship; historical homeland of Ghengis Khan.
Map: Nei Meng Gu AR
3. Ningxia Hui
Capital city: Yinchuan
Population: 5.9 million
Designated ethnic minority: Hui
Famous for: the Western Xia tombs; desert scenery.
Map: Ningxia Hui AR
Capital city: Urumqi (or Ulumuqi) - pronounced "woo loo moo chee"
Population: 19.6 million
Designated ethnic minority: Uyghur ("wee ghur")
Famous for: lying in China's west, Xinjiang looks more Central Asian than East Asian; Karakoram Highway; stops along the ancient Silk Road, desert scenery.
Map: Xinjiang AR
Capital city: Lhasa
Population: 2.7 million
Designated ethnicity: Tibetan (unlike in the other ARs, the Tibetans are actually the majority population despite the government-supported migration of Han Chinese to the area).
Famous for: Tibetan Buddhism (seat of the exiled Dalai Lama); Mt. Everest and Himalayan scenery.
Map: Tibet AR