Technically it is a "special administrative region" in China. However it has its own political and economic systems so is usually classed as a country.
Hong Kong island was and could still be british colony helping the uk economy but Maggie Thatcher in 1984 sold it down the river cause the lease on the new terrartories was only a 100 years and had to be returned in 1997 and wanted to keep china sweet.
The Deal was to allow Hong kong now a province of China to be self democratically governing for 50 years. Luckilty china has left it alone as they know that Hong kong is the gate way busines Hub to south east asia for trade. I was in hong kong last year and their 999 services like ambulance and fire brigade gear is the same as the uk, even the police motorbike helmets Also all signs are English and Cantonese, Also you will find alot of british stores there, Boots, Tescos etc
Hong Kong is a province/city. Like New York is a city/state. I find that most chinese people I know are actually from Hong Kong. A kid in my class who was born there goes back every Chinese New Year.