https://news.cctv.com/2021/12/21/VIDExd ... 1221.shtml
The move is part of the initiative to create a Leisure-oriented Hainan Free Trade Zone, covering the while Hainan Island. It is expected that trade between foreign countries and Hainan will not be subjected to tariff, however when goods and people move between Hainan and Mainland China, they will need to receive custom checks and pay the appropriate tariff.
Some have compared the arrangement to Shenzhen's check points walled off from rest of China in 1990s.
I guess it qould be interesting to see what it mean in the current era when most policies in China nowadays are generally going back against the trend of reform and opening uo/