Cost per click (CPC) is a pricing model used in online advertising, where the advertiser pays a certain amount of money each time a user clicks on their ad. The cost per click is determined by the advertiser and can be based on various factors, such as the target audience for the ad, the keyword that the ad is targeting, and the competition for the ad. Advertisers typically aim to minimize the cost per click while maximizing the performance of their ads.

Effective cost per click (eCPC) is a measure of the average cost per click that is achieved across an advertising campaign. It is calculated by dividing the total cost of the campaign by the total number of clicks that the ads received. eCPC can be useful for comparing the performance of different advertising campaigns and for making data-driven decisions about how to optimize the campaign to improve its performance.