The Hang Seng Index (HSI) is comprised of the 50 biggest stocks traded on the Hong Kong Stock Exchange.
The Hong Kong stock market is much different than that of China, in that foreign investors are allowed access and the index is calculated on a free floating cap-weighted basis.
It tracks the 50 biggest companies on the Hong Kong Stock Exchange, and is a better barometer for measuring overall performance of companies from the region.
What is the Shanghai Composite Index?
What is the MSCI World?