As we have already discussed, a lead is when you get someone to show some interest in your offer. In the off-line world, perhaps you ask them to send a self-addressed, stamped envelope for more information? or to calll an 800 number? or to visit a web-site. That is a lead. They have viewed your ad (an impression) and then taken some kind of action to show that they are interested. A click is one form of a lead. However, in the online world, we generally call a click a click and don?t call a lead a lead until they give us some contact information. So in the offline world, if someone called an 800 number? that would be a lead. However, in the online world, most people don?t think of it as a lead when they just click? only when they provide some contact information.