If you mean the green equivilant of Digg, its fairly simple,
If you have a news story that you think fits the genre then you sign up and submit the story. Other users can then decide to "hugg" the site which basically adds one to its score, the more huggs a site gets the higher it appears on the front page.
with digg a good story can attract thousands of diggs, and I'd imagine many of the hosts on here can tell you if you have a hot story you can experience the "slashdot" effect (a similar site again) where the volume of visitors crashes servers etc.
Its basically a good marketing tool assuming you have "interesting" stories.
hth a bit
