When there is a post by someone, you can give them a 'good' or 'bad' kudos. The only thing is, is that when you give 'bad' kudos, they also count against you.
It's just a way of telling another poster you really like/dislike what they have to say.....
Someone else may have a better explaination.......
JUST found this...posted by El_Tino -
"Kudos are a way for you, the members of TFS, to help shape what kind of posts you want to see on TFS!
It also provides feedback to posters on what other people think of their post.
You are able to give both positive and negative kudos. When a post gets positive kudos, the number of points for the post will increase 20% of the time (and whoever posted it will get that point).
If a post receives enough negative kudos it is automatically removed from the site and any points earned by posting it are deducted from the posters point total.
Each day you have a limited number of kudos depending on your user level. Currently it is 10 kudos per day for all normal members with positive points.
So, give positive kudos to good posts and negative kudos to spam or flaming posts!"
Its a system that has been created so you are able to tell other members you like their posts or agree with what they are saying, and give a reason why!