English language level explanation

[marcipaans]

Long story short - I need to make a study material for my english class and I just found a perfect website. The only problem(though insignificant) is that I got no clue what do these numbers mean. What level of english do they represent?
There are 100; 800; 1200; 3000 and 4000 Level. Well Level 100 is obviously for complete beginners who are learning the very basics of english language. But how about others?

Here is the website - http://www.nonstopenglish.com/allexe...iplechoice.asp

[k3lster]

If you put your cursor over the numbers for sometime, you can see what it means.