Cost Per Impression (CPI) is a marketing metric that measures the cost an advertiser pays for each time their ad is displayed, regardless of whether it is clicked. This metric helps businesses understand the effectiveness of their advertising campaigns by evaluating how much they spend to reach potential customers. CPI is commonly used in digital advertising, particularly in platforms like Google Ads and Facebook Ads. Advertisers can use this information to optimize their budgets and strategies, ensuring they get the most exposure for their investment while reaching their target audience effectively.