In the context of display advertising, click-through rate (CTR) and cost-per-click (CPC) are two important metrics that are often used to measure the effectiveness and efficiency of an advertising campaign. CTR is a measure of how often users who see an ad actually click on it, while CPC is a measure of how much an advertiser pays for each click on their ad.

Auction-based advertising, in which ad space is bought and sold through a bidding process, is directly related to both CTR and CPC. In an auction, advertisers can bid higher or lower for an ad space based on their desired CTR and CPC. For example, if an advertiser is willing to pay more for each click and expects a higher CTR, they may bid higher in the auction to secure the ad space. On the other hand, if they have a lower budget or are less confident in their ad's ability to drive clicks, they may bid lower in the auction. In this way, the auction process can impact both the CTR and CPC of an advertising campaign.