Can Someone please tell me about the new karma system.. I didn't understand especially the part

"Karma may also go down as well as up depending on everyone else's perceived quality of that comment which users will soon be able to up or down vote on. So if you've been spamming stories and blogs with useless comments, I would highly suggest that you start deleting them now  "

yeah.. that part.. please help me.. Sorry, english is not my first language, so to understand this things is hard for me :(

Thanks~!! *bow*