HSK is a Chinese capability test for non-local speakers of Chinese. The test is what could be compared to the English TOEFL test. It is composed of oral Chinese and goes from level 1 (HSK 1) to even out 6 (HSK 6), HSK 6 is the most troublesome, however can be utilized as an authority capability. For instance, if going after a position that requires you to speak Chinese, they might ask you for HSK level 5 or above.