Just take a look which ad network use by app developer's to earn revenue

AdMob is a mobile advertising platform developed by Google that enables mobile app developers to monetize their apps by displaying targeted ads to their users. With AdMob, app developers can earn revenue by showing text, display, and video ads on their app, and get paid whenever users interact with those ads.

To start using AdMob, you need to sign up for a free AdMob account and integrate AdMob SDK into your mobile app. Once this is done, you can create ad units and set up ad mediation to display ads from multiple ad networks to increase revenue.

AdMob uses machine learning models to show users ads that are relevant to their interests and behavior, thereby increasing the chances of them engaging with the ads. The revenue earned from AdMob depends on various factors such as the types of ads displayed in your app, the number of users using your app, and the engagement level of your users.

It's essential to follow Google's policies and guidelines for AdMob to ensure that your app complies with the platform's standards and to maximize your earnings.