I heard about Klout a while ago via friends on Twitter, and to be honest I still don't completely understand it!! Basically it looks at all your profiles that you link to it. I have Facebook, twitter, and my blog linked to it, and it gives you a score based on how influential it thinks you are (well I think that's how it works!). You then get given a score, mine is currently 56. You can then give Klout to your friends on subjects and vice versa.
One of the benefits of Klout is Klout perks, up until recently I hadn't received any and a certain person (yes Sarah I am talking about you!) seemed to be getting lots. Then my luck or something changed, and since then I've had a few. The first two were money of some websites, which as of yet I haven't yet used. Then the most recent two were pretty cool.
I was given a free product or sample because I'm a Klout influencer. I am under no obligation to receive the sample or talk about this company. I get no additional benefits for talking about the product or company.