It translates literally to "Chinese Proficiency Test" : Hanyu Shuiping Kaoshi wikipedia.org
The Hanyu Shuiping Kaoshi, (simplified Chinese:汉语水平考试; traditional Chinese: 漢語水平考試;pinyin: Hànyǔ Shuǐpíng Kǎoshì), abbreviated as HSK, is the People's Republic of China's only standardized test of Standard Chinese language proficiency for non-native speakers, namely foreign students, overseas Chinese, and members of ethnic minority groups in China.