a special administrative region (sar) is a region in china that has a high level of autonomy, or a lot of power to rule itself. there are two sar's in china, hong kong and macau. unlike other regions in mainland china, sar's have a basic law, a constitution that is different from that of the people's republic of china (prc). basic law allows hong kong and macau to have freedoms that are not in the rest of china, like freedom of religion, freedom of speech, freedom of the press, freedom of assembly, and freedom to petition. basic law also allows the sar's to decide the economic rules of their region, which is why the economies are a lot less controlled in hong kong and macau than in mainland china, as well as giving them the freedom to choose who to let into their own regions without needing a visa. as a result, hong kong and macau have their own currencies, passports, official languages, etc. this is commonly known as the "one country, two systems" policy.