In AdMob, ad campaigns are managed in the Campaigns tab. You can set the type of campaign and the type of goal for each campaign. There are two types of campaigns available:
House ad campaigns promote your own apps and websites. House ad campaigns are cross-promotion campaigns that serve ads to an app using a developer's own inventory for free. For example, an app that shows ads for the developer's other apps, encouraging users to try them out.
We suggest using the mediated ad goal type and use Google optimized for backfill for house ad campaigns.
Direct sold campaigns are created for an advertiser. Direct sold campaigns are campaigns in which you sell advertising inventory directly to an advertiser. Billing is handled outside of the AdMob platform. These campaigns can include traditional display advertising or app install campaigns.
You should discuss with your advertiser which goal type should be used for the campaign.