CPI, or cost per install, is a pricing model used in mobile app advertising, including Google Ads. In the CPI model, advertisers pay a fixed amount for each install of their app that is attributed to their ad campaign.

For example, if an ad campaign has a CPI of $2.00 and it results in 100 installs of an app, the cost to the advertiser would be $200.00 (100 installs x $2.00 CPI). If the ad campaign results in 200 installs, the cost would be $400.00, and so on.

CPI is often used as a measure of the effectiveness of an ad campaign, as it provides a way to compare the cost of the campaign to the number of installs it generates. Advertisers may choose to use the CPI pricing model if their primary goal is to drive app installs and increase their user base.

In Google Ads, advertisers can choose to bid on CPI or use a different pricing model, such as cost per click (CPC) or cost per thousand impressions (CPM). The choice of pricing model will depend on the specific goals and objectives of the ad campaign.