It’s an International Test of Chinese Language Proficiency, Hanyu Shuiping Kaoshi. It reminds TOEFL by its’ structure consisting of Listening, Grammar, Reading and Writing. It’s a state test to certify a level of Chinese language proficiency of foreigners, emigrants and national minorities.
A certificate allows you to seek a job or enter a Chinese University. It also gives you a priority while looking for a job in Chinese company or company cooperating with China.
You can choose basic, beginning, intermediate or advanced level. The certificate is good as long as you like. You can pass a test as many times as you want to get a certificate of higher level.
Nowadays HSK includes series of tests for Kids, Business, Secretaries, Tourism. Kids under 15 years old can pass a Special test. Other specific tests were developed on the base of the standard HSK test to satisfy demands of Chinese language development.