You get 1 kudo for every reply to a thread. You get 2 Kudos for every new thread you start.
Kudos are just a "for fun" thing. They are a way to show appreciation for help that someone had given you or congratulations to some one for something special.
You can donate as many Kudos as you want to someone by clicking on the "donate" under a profile to the left of a post. For esample, I just donated some to you to bring you to an even 100. See how it works?
Edit: Thanks Meridith....I was trying to find that thread but couldn't locate it. You posted it while I was typuing my reply