Variously known by the term pay-per-click (PPC), cost-per-click (CPC) is a billing method used by online sites based on the number of times a visitor clicks on an advertisement. As an alternative, cost-per-thousand (CPM) is based on the number of impressions, or viewers, in thousands, no matter whether each viewer clicks on the ad or not.
As an example, a website that has a CPC rate of 60 cents and delivers 1,000 click-throughs would charge $600 ($0.60 x 1000). The amount an advertiser pays for a click is usually determined either by a formula or by a bidding process.
Setting cost-per-click (CPC) bids means that you pay for every click on your ads. In campaigns with CPC bids, you set a maximum cost-per-click bid - or simply "max CPC" - which is the highest amount you're willing to pay for a click on your ad.