Hong Kong is a former British colony that reverted back to Chinese control. It is composed of several areas that all maintain a special administrative region status meaning that as an American you can head there without a visa.
Across the bay from Hong Kong is Kowloon, or as I like to call it “the affordable Hong Kong.” Lots of night life, great restaurants, interesting things to see, and only a 10 minute subway ride under the bay from Hong Kong.
Lantau Island is a tourist area off of the Hong Kong airport area. This island has a huge Buddha statue at the top and cable cars to take you all over the island, great for hiking.
The New Territories are a parcel of land in the hills to the north of Kowloon. There are some great seafood places here where you can get the most amazing fresh catch that you have ever seen, cooked to order and brought to your table.