It's broken into six levels, each having a new block of characters to learn.
With clear difficulty levels and government backing, it's the clear model to use to learn the major language of China.
As I understand, registration must be done in advance, and there are set dates when testing occurs. (info in Chinese)
My knowledge will be clearly separated by HSK level. Hopefully this will help the next person.
HSK level 1 -- Beginner
- HSK level 2 -- Tourist
- HSK level 3 -- Conversation
- HSK level 4 -- Discussion
- HSK level 5 -- Expert
HSK level 6 -- Academic