Hong Kong is now part of China (as it also was until it was ceded to the Britains in 1842). It is still not considered to be part of mainland China but is a Special Administrative Region. Some obvious differences are that people drive on the left side and that the currency is the Hong Kong dollar. For western companies interested to set up shop in China, Hong Kong can be an attractive location. English is widely spoken and it is easy to register a company and to transfer money across the boarder. Hong Kong can also be a stepping stone to further investment in mainland China.