Cost per Engagement is a pricing model that is based on a predefined engagement metric. This metric can be any kind of action that the advertiser wants the user to execute e.g. “get to level 5” within a mobile game. In this example the advertiser would only have to pay when a user is downloading the app and at least reaches level 5 within the app.
This pricing model is very suitable for all advertisers who want to generate high-quality users. In this form of advertising, engagement of the user with the app is a lot more intense. Therefore, these users hold a way higher value for the advertiser than other users who just download and install the app.
Accordingly, the CPE pricing model generates users that have a way higher Customer-Lifetime-Value (CLTV) for a company than cost-per-click because they are much more likely to use the app for a long time period.
You can find a detailed overview of all pricing models available in this article.