Hong Kong and Macau are a sort of countries, not totally free from Chinese influence, but they do have a sort of autonomy, with their own passports, police and currency. CGP Grey went on to investigate the strange history of wanna-be states and the conclusion is that we won’t know if they are really free countries until… until the history will tell us.
Hong Kong and Macau are geographically part of China, but have all the perks of a full-fledged country. In the 15th century Portugal showed up in China and bought the island of Macau by bribing the Chinese officials that were living there. Later the British Empire showed up fought China in the Opium Wars and thus Hong Kong became rules by the UK.
This way, although Macau and Hong Kong are part of China, they exist through the influence of the former empires and have their own parliament, government, police, schools, currency.