An autonomous region, used in the context of China, translates for zizhiqu (自治区 zìzhìqū), which are province-level divisions with a designated ethnic minority, and are guaranteed more rights under the constitution than provinces. For example, they have a chairman (where regular provinces have governors), who must be of the ethnic group as specified by the autonomous region (Tibetan, Uighur, etc)
Autonomous regions were established after communist takeover, following Soviet nationality policy. There are five in total.