This means that you, as the end-user, will think that you are clicking on one thing, when in reality you're clicking on another. This probably doesnt sound like much of a big deal on the surface, but when people visit your website and see an innocent looking ENTER HERE doorway page, as they click - they are really adding money to your affiliate marketer (Google Adsense, Adbrite, etc) account because in the backround, they don't know that when they clicked ENTER HERE, they actually clicked on a hidden affiliate banner, Google Text ad, etc. I should note that clickjacking has many alternative uses, hence clickjacking can be used to secretly divert traffic, automate browser plugin or software installs etc.
