Cost per Click (CPC) is one of the crucial factors in pay-per-click (PPC) marketing campaigns, like Google AdWords, for example. CPC is the price the advertiser pays for each click the visitors make on their advertisement. What this means is that the advertiser is charged only when the users interact with their ad. In a large majority of cases, CPC is smaller or equal to the maximum bid made by the advertiser. This is because the CPC is actually the average value of bids in the PPC auction. What this means is that CPC depends quite a lot on your ad rank (as well as the ad rank of your closest competitor), your maximum bid, and the Quality Score.